Genetics Flashcards
Which molecule contains the coding information in a cell?
Nucleic acid
Which scientist discovered genes and the inheritance of characteristics?
Gregor Mendel
How many chromosomes does a normal human have?
46
People suffering from Down’s syndrome have an extra chromosome number of?
They have two copies of chromosome 21
Evolution is driven by?
Natural selection
How many genes found in human dna
25,000
What does dna stand for?
Deoxyribonucleic acid
What does rna stand for?
Ribonucleic acid
What are nucleic acids (biopolymers) made up of?
Nucleotides (monomers)
What is mRNA?
Messenger nucleotides convey genetic material from the DNa to the ribosome where they specify the amino acid sequence of protein products for gene expression
Which nucleic acid contains coding info for protein synthesis?
mRNA
What is the prenatal screening technique for chromosomal abnormalities?
Amniocentesis
What are pluripotent stem cells?
Pluripotent = cells can become one of three main things: cardiac muscle, neural cells or blood cells.
Stem cells = they have the ability to divide and create identical copies of themselves called self renewal, they can also divide to form cells that make up every type of tissue in the body Most pluripotent stem cells talked about are embryonic or ips cells(induced pluripotent cells genetically modified to behave like embryonic stem cells)
diagram shows the transcription and translation processes in three basic steps.
First, DNA is transcribed into RNA, and then the new mRNA is processed to form a mature mRNA transcript. Finally, the mature mRNA is translated into a protein.
describe the transcription process in gene expression
In the first step, the information in DNA is transferred to a messenger RNA (mRNA) molecule by way of a process called transcription. During transcription, the DNA of a gene serves as a template for complementary base-pairing, and an enzyme called RNA polymerase II catalyzes the formation of a pre-mRNA molecule, which is then processed to form mature mRNA . The resulting mRNA is a single-stranded copy of the gene, which next must be translated into a protein molecule.
what cell is totipotent?
single cell embryo
totipotent: ability of single cell to form a complete body. plants are totipotent and so are animals till the embryonic stage but not after birth
what cells are pluripotent?
embryonic and ips (induced pluripotent cell from an adult or child)
what cells are multipotent?
cord blood stem cells, placental stem cells, adult stem cells
multipotent: Multipotent cells can develop into more than one cell type, but are more limited than pluripotent cells
what animal and plant has higher chromosones than humans?
chickens and bracken
what happens in a plymerase chain reaction or a pcr?
Polymerase chain reaction, or PCR, uses repeated cycles of heating and cooling to make many copies of a specific region of DNA. First, the temperature is raised to near boiling, causing the double-stranded DNA to separate, or denature, into single strands. When the temperature is decreased, short DNA sequences known as primers bind, or anneal, to complementary matches on the target DNA sequence. The primers bracket the target sequence to be copied. At a slightly higher temperature, the enzyme Taq polymerase, shown here in blue, binds to the primed sequences and adds nucleotides to extend the second strand. This completes the first cycle. In subsequent cycles, the process of denaturing, annealing and extending are repeated to make additional DNA copies. After three cycles, the target sequence defined by the primers begins to accumulate. After 30 cycles, as many as a billion copies of the target sequence are produced from a single starting molecule.
what is a cell?
The basic unit of structure and function in living organisms
where do new cells come from?
they can only come from existing cells
as cells grow and divide what do they need a new copy of?
DNA
Before division the DNA in each chromosome is replicated
how many chromosomes in each somatic cell do humans have?
46
Eg Human
22 pairs autosomes + XY if male
or XX if female
= Total 46
why do cells divide?
- Growth
- Reproduction
- Replacement of dying cells – skin, RBC
- Reproduction in multi-cellular organisms – gamete formation (meiosis)
why dont cells just get bigger instead of dividing?
surface area: Volume ratio constraints
what cell is this?
plant cell
The plant cell is a type of eukaryotic cell , with different characteristics that differ from animal cells , fungaland other realms of the living:
the presence of the cell wall composed of cellulose (a polymer whose basic unit is the glucose , protein and, as a result of modifications, from lignin , suberin …) and related plasmodesmata , channels in the cell wall through which the cells of the plant are in communication with each other.
the plastids , and especially the chloroplasts that, thanks to the chlorophyll allow plant cells to produce monomers of sugar (glucose) and oxygen from the CO2 exploiting the ‘ solar energy , said process is defined as photosynthesis .
characterizing the presence of numerous vacuoles (organelles but not intracellular cavity, surrounded by a membrane, called the tonoplast ) that occupy a large part of the cell and whose main function is to keep the cell turgor . Are involved in the control of the passage of molecules from the blood to the cytosol, in the maintenance of the pH optimum of the cytosol, and perform functions of reserves of various substances.
the absence of centrioles typical animal cell.
what is this?
cell nucleus
•Genetic information is contained within chromosomes
– threadlike structures composed of DNA,
– present in the nuclei of cells
– passed to daughter cells during cell division
where are chromosones present?
in the nucleus of cells
what are chromosones?
–threadlike structures composed of DNA,
– present in the nuclei of cells
– passed to daughter cells during cell division
what is a teleomere and centromere?
each long bit of the ‘x’ shaped chromosone is called a chromatid
centromere: the point on a chromosome by which it is attached to a spindle fibre during cell division as the central region where the two chromatids are held together and form an X shape..
Telomere: The end of a chromosome. The ends of chromosomes are specialized structures that are involved in the replication and stability of DNA molecules. A telomere is a length of DNA that is made up of a repeating sequence of six nucleotide bases (TTAGGG).
are most eukaryotic species diploid or haploid?
diploid
what are Homologous Chromosomes?
pairs of autosomes where one from each pair derived from each parent
what is a gamete?
sex cell; sperm or egg
define recessive trait
trait that will only appear in the phenotype if organism inherits two of them; covered up by the dominant gene
what is an autosome?
Any chromosome other than the sex chromosomes.
what is a base
One of four chemicals which make up the ‘rungs’ of DNA; A;T;C;G
what are these sequences for?
e.g. CCAAGTAC.
These sequences are the code for genetic information
what are the bases that make up ATGC?
adenine is the “A”.
“G” for guanine,
“C” for cytosine,
“T” for thymine.
Adenine always pairs with thymine. Cytosine always pairs with guanine.
Adenine always pairs with?
Thymine
Cytosine always pairs with?
Three hydrogen bonds attract the following base pair
G and C
In transcription, the poly-A tail:
Protects against 3’ exonuclease
what mitosis phase is this?
Anaphase
what are somatic cells?
–are major components of most organisms–replicate through mitosis
–
– have 2 copies of each chromosome,
(46 in humans)
a condition known as diploid (or 2n)
what are Germ cells (gametes)?
–pass on the genetic information to the progeny
–
–formed by meiosis
–
–contain only one chromosome from each pair,
( 23 in humans)
–a condition known as haploid (or n)
Why 2 sets of chromosomes?
Diploid 2n
•Can carry more genetic variation•If a gene on one copy is faulty there is a back-up, heterozygote often viable.
•
•More potential for evolution if environment changes
•
•Mixture of characteristics from both parents
describe the cell cycle
- interphase
- mitosis
- cytokenesis
Describe interphase
non-dividing, metabolically active.
At least 90% of cycle, composed of:-
G1 Phase à 1st growth phase,
(Restriction point.)
S Phase à DNA duplicated
G2 Phase à Final growth phase
which part of the cell cycle is 90%
interphase
what is mitosis?
- mother cell produces two daughter cells, both identical to the mother cell.
- Used for growth and repair, tissues vary:-
Human skin cells divide throughout life
Liver cells divide in order to repair damage
Nerve cells very specialised, once mature do not divide, damage usually permanent
what are the phases of mitosis?
•Prophase
•
•Metaphase
•
•Anaphase
•
•Telophase
what does interphase look like?
not yet started to split
what does prophase look like?
- Chromatin condenses, chromosomes become visible.
- Centrioles separate, moving to opposite sides of the nucleus.
- Centrioles start to make the mitotic spindle out of microtubules.
- Nucleolus disappears.
what does metaphase look like
- Nuclear membrane fragments.
- Kinetochore is formed at the centromere.
- Microtubules attach at the kinetochores, the two kinetochores face in opposite directions.
- Chromosomes align on equator of cell, called metaphase plate.
what does anaphase look like?
centrimeres split
what is teleophase?
•Chromatids have reached their destination and begin to elongate back to long thin chromatin.
•Nuclear membrane and nucleolus reform
•Formation of cleavage furrow where cell starts to split.
Cytokinesis; division of the cytoplasm
what is cytokenesis?
division of the cytoplasm
alternate images of interphase prophase anaphase teleophase
another image of the phases of mitosis
how many haploid gametes in the human life cycle?
23 = n (half of 46 2n=46 which is diploid)
23
which half of the human life cycle is haploid?
meiosis -> egg and sperm -> fertilisation
which half of the human life cycle is diploid?
zygote -> mitosis + development -> adults -> ovaries and testes produce egg and sperm cell which are haploid
Fusion of an ovum and sperm produces a
zygote (diploid 2n)
Zygote divides and grows to adult by
mitosis
what does meiosis produce?
•Produces 4 daughter cells which have half the original chromosome number of mother cell.
(One from each homologous pair.)
Used to produce haploid (n) gametes.
Reduction division
•These daughter cells are not identical to the mother cell or each other.
Reduction division
These daughter cells are not identical to the mother cell or each other
what is reduction division and is it a part of meiosis or mitosis?
Reduction division
These daughter cells are not identical to the mother cell or each other
part of meiosis
how many stages does meiosis consist of?
two phases:
Meiosis I – Prophase I, Metaphase I, Anaphase I, Telophase I
Meiosis II - Prophase II, Metaphase II, Anaphase II, Telophase II
and it Requires two divisions of the nucleus and cell
what is a tetrad
4 haploid pollen grains in a tetrahedral shape
what is chiasmata
the point where two homologous non-sister chromatids exchange genetic material during chromosomal crossover during meiosis
forms in prophase 1
what phase is this?
interphase 1 in meiosis
what phase is this?
prophase 1 in meiosis
what phase is this?
metaphase 1 meiosis
what phase is this?
- Nuclear membrane reforms
- Original cell divides by Cytokinesis
- Only one set of chromosomes present in each new cell
- Known as reduction division – haploid cells produced
teleophase 1 meiosis
what phase is this?
prophase 2
meiosis
what phase is this?
anaphase 2 meiosis
what phase is this?
teleophase 2 and cytokenesis 2
note that there are now 4 daughter cells
is mitosis or meiosis a part of asexual reproduction and what are the benefits of asexual reproduction?
mitosis is a part of asexual reproduction
–easy, rapid, effective way to reproduce
–useful in stable environment
–lack of genetic diversity among offspring
is mitosis or meiosis a part of sexual reproduction?
what are the benefits of sexual reproduction?
meiosis
–promotes genetic variability, unique combinations
–useful in dynamic environment
what is Euploidy
gain or loss of whole sets of chromosones
cells with an exact multiple of the haploid number e.g.
•2 sets = polyploidy 3n = triploid, 4n = tetraploid, 6n = hexaploid
what is Aneupoidy?
Gain or loss of single chromosomes
Aneuploidy are cells with an uneven number of chromosomes, but not an even set. So, aneuploidy like trisomy 21 would be the same as diploid + 1 chromosome. Turner syndrome in humans is a case of aneuploidy because it’s diploid - 1 or 45 chromosomes…
•Aneuploidy = gain or loss of whole chromosomes. 2n + 1 or 2n – 1
This is usually due to a problem in cell division, usually in production of gametes,
but can be very early in development from zygote, leading to mosaic conditions
what is monoploidy?
- Normal for gametes.
- Individuals that arise from unfertilised eggs. Eg males of certain insects ; - drones, ants, wasps.
- Some fungi are haploid, plus lower plants.
- Rarely seen in normal diploid organisms, due to frequent presence of lethal mutations, no spare copy, - usually fatal.
what disorder does this karyotype show?
Patau syndrome
The process of introducing recombinant DNA into a plasmid is called:
Cloning
In PCR why is DNA heated to over 95 degrees centigrade
to denature the double stranded DNA
what is polyploidy?
containing more than two paired (homologous) sets of chromosomes.
what happens with polyploidy in humans?
•Almost always lethal
3n; approx 15% spontaneous abortions; plus in 1/10,000 live births, but most die within a month, large head + serious abnormalities.
4n; approx 5% spontaneous abortions, rarely born alive, soon die.
what happens with polyploidy in plants?
•Does not have such severe consequences for plants; can be self fertile or reproduce asexually.
Bramley apple, triploid sterile.
Wheat hexaploid.
Strawberry octopoid.
Often associated with larger fruit in cultivated plants.
Plus some wild grasses eg Spartin
what is this an example of?
normal meiosis
All gametes hapoid, fertilisation:- n + n = 2n zygote
what is this an example of?
Non disjunction Meiosis 1
what is Nondisjunction during meiosis 1
- Nondisjunction of homologous pairs of chromosomes in anaphase of meiosis 1 leads to;
- 4 abnormal gametes; 2 with two copies of the chromosome, and 2 with none.
- Fertilisation 2n + n = 3n; tripoid
zero + n = n; monoploid
what is this an example of?
Non disjunction Meiosis 2
what does nondisjuntion durin meiosis 2 mean?
- Nondisjunction of chromosomes into chromatids leads to;
- 2 abnormal gametes and 2 normal gametes.
Nondisjunction happens when a pair of sex chromosomes fails to separate during the formation of a sperm (or egg). When sperm with no X chromosome unites with a normal egg to form an embryo, that embryo will have just one X chromosome (X rather than XX). As the embryo grows and the cells divide, the X chromosome will be missing from every cell of the baby’s body.
what are karyotypes for?
A karyotype is simply a picture of a person’s chromosomes. In order to get this picture, the chromosomes are isolated, stained, and examined under the microscope. Most often, this is done using the chromosomes in the white blood cells. A picture of the chromosomes is taken through the microscope.
they are useful for
- To look at chromosomes structure and number.
- Dividing cells used, chromosomes shorter and more easily seen with the microscope.
- Autosomes arranged and numbered in order of size, followed by sex chromosomes.
is this karyotype of a woman or a man?
female
is this kayrotype of a woman or man?
what is down syndrome also known as?
Trisomy 21
what genetic disorder is this?
downs syndrom or trisomy 21
what genetic disorder is this?
patau syndrome or trisomy 13
what genetic disorder is this?
Patau syndrome or trisomy 13
note the three chromosons under 13
what genetic disorder is this?
trisomy 18 or edwards syndrome
what genetic disorder is this?
trisomy 18 or edwards syndrome
what disorder is this?
Turner syndrome X0
itis caused by a missing or incomplete X chromosome. People who have Turner syndrome develop as females.
it happens through non disjunction
the mother must pass the condition on, a father cannot have the condition because he only has one x chromosone
what genetic disorder is this?
Klinefelters
Male individual
most often occurs when the genetic material in the egg splits unevenly. But it can also occur when the genetic material in the sperm splits unevenly. Even though Klinefelter syndrome is a genetic disorder, it is not passed down through families.
what other reasons are there for intersex conditions besides chromosone number?
•Abnormal differentiation of gonads
•
•Phenotypic sex ambiguous or not in agreement with chromosomal sex, hermaphrodites
Abnormalities which cause an increase in androgen and testosterone synthesis may confer a competitive advantage. Eg. Congenital Adrenal Hyperplasia
what is this?
Mosaicism
if an organism is going to be used in genetic study what features must it have to be a good candidate?
Easy to grow.
A number of easily discernable characteristics.
Controlled matings possible.
Large numbers of progeny produced.
Short generation time.
e.g. fruit flies (4 chromosones)
what is drosophila melanogaster a good candidate for genetics testing?
•Egg – adult 7-10 days
•100 eggs per day
•Only 4 chromosomes
•Easy to anaesthetise
•Easily discernable characteristics
Easy and cheap to maintain in laboratory
fruit fly
what did Gregor Mendel work on?
- Worked on pea plants.
- He did not know about genes, but postulated that ‘factors’ controlled the inheritance of characteristics,
- and some factors were stronger than others.
Looked at characteristics with discontinuous variation, no intermediate forms.
Single gene pair controls.
- Height; Tall/Short
- Flower colour; Purple/White
- Seed shape; Round/Wrinkled
- Seed colour; Yellow/Green
what is a genotype
genetic make-up of an organism.
what is a phenotype?
characteristics that can be observed or measured
whos experiment is this?
Gregor Mendel
he found out a particular flower colour dominated when crossing pea plants
what does this pedigree symbol mean?
heterozygotes for autosomal recessive
what does this pedigree symbol mean?
dizygotic non identical twins
what pedigree symbol is a male?
square
what pedigree symbol is female
circle
single sex gene defects can be
- Autosomal dominant
- Autosomal recessive.
- Sex linked dominant
- Sex linked recessive.
Sex linked conditions can be carried on the X or Y chromosome, usually on the X
what is meant by autosomal gene inheritance?
Autosomal means sex of individual has no influence on inheritance of disease.
what happens in autosomal dominant inheritance
•an abnormality occurs when only one of the genes from one parent is abnormal
•
•if the parent has the disorder, the baby has a 50 percent chance of inheriting it
in autosomal disorders how many copies of a defective gene are needed to pass the condition along
Individual needs to inherit only one copy of the defective gene
3 examples of autosomal disorders
. Huntington’s chorea.
- Achondroplasia.
- Marfan syndrome
what is huntingtons caused by?
- Caused by stutter on DNA.
- Excessive number of repeats of CAG on
chromosome 4.
- Brain deteriorates in middle age.•If the parent has the disorder, the baby has a 50 percent chance of inheriting it.
- 12 in 100,000 approx.
what is achondroplasia
Defect on chromosome 4.
Fault in fibroblast growth factor receptor.
80% patients due to new mutation.
More likely if father over 35. 1/25,000
imperfect bone development causing dwarfism
what is marfan syndrome
Defect on chromosome 15, connective tissue disorder.
causing long limbs and heart defects
arachnodactyl y fingers
what is Loeys-Dietz
autosomal dominant
similar to marfan syndrome
High risk of sudden death due to rupture of aortic aneurysm.
Joint hypermobility
Club foot
Curved spine
etc
what does heterozygous mean?
individuals who are heterozygous for a certain gene carry two different alleles
what does homoszygous mean
individuals who are homozygous for a certain gene carry two copies of thesame allele
name three programs for bioinformatics
BLAST
G query
TRANSLATE
what experiment did Avery, Macleod and Mcarty do?
experimental demonstration that DNA is the substance that causes bacterial transformation.
linking into Griffiths experiement they did studies on the chemical nature of the substance inducing transformation of pneuococcal types.
At that time it was thought protein might be the hereditary material. In their paper of 1944, Avery and his colleagues suggest that DNA, rather than protein was the hereditary material of bacteria, and could be analogous to genes and/or viruses in higher organisms
they discovered that the active factor when transforming dead cells into live cells is DNA
what was griffiths experiment?
he proposed that material in dead bacterial cells can transform living bacterial cells, a chemical substance from one cell is capable of genetically changing another cell.
He concluded that the type II-R had been “transformed” into the lethal III-S strain by a “transforming principle” that was somehow part of the dead III-S strain bacteria.
Today, we know that the “transforming principle” Griffith saw was the DNA transformation of the III-S strain bacteria. While the bacteria had been killed, the DNA had survived the heating process and was taken up by the II-R strain bacteria. The III-S strain DNA contains the genes that form the shielding polysaccharide part from attack. Armed with this gene, the former II-R strain bacteria were now protected from the host’s immune system and could kill the host.
The exact nature of the transforming principle (DNA) was confirmed in the experiments done by Avery, McLeod and McCarty and by Hershey and Chase.
this showed DNA transformation
r strain mouse lives (non virulent)
s strain mouse dies (virulent)
heat killed smooth strain mouse lives
heat killed smooth strain and r strain mouse dies (living s strain found in the mouses heart)
what is electropheresis?
the separation of DNA fragments using agarose gel electrophores
In the Hardy-Weinberg equilibrium, 2pq represents:
The predicted frequency of heterozygous individuals
The Hardy–Weinberg principle, also known as the Hardy–Weinberg equilibrium, model, theorem, or law, states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences. These influences include mate choice, mutation, selection, genetic drift, gene flow and meiotic drive.
The simplest DNA end of a double stranded molecule is called a
blunt end
In a blunt-ended molecule both strands terminate in a base pair. Blunt ends are not always desired in biotechnology since when using a DNA ligase to join two molecules into one, the yield is significantly lower with blunt ends. When performing subcloning, it also has the disadvantage of potentially inserting the insert DNA in the opposite orientation desired. On the other hand, blunt ends are always compatible with each other.
when is a stick cut end used?
They are most often created by restriction endonucleases when they cut DNA. Very often they cut the two DNA strands four base pairs from each other, creating a four-base 5’ overhang in one molecule and a complementary 5’ overhang in the other. These ends are called cohesive since they are easily joined back together by a ligase
Looking at the following PCR cycles, select the PCR cycle that has all the correct temperatures to successfully produce a PCR product
950C @ 30 seconds 600C @ 60 seconds 720C @ 120 seconds 30 cycles
what is recombiant DNA?
Recombinant DNA (rDNA) molecules areDNA molecules formed by laboratory methods of genetic recombination (such as molecular cloning) to bring together genetic material from multiple sources, creating sequences that would not otherwise be found in biological organisms.
A restriction enzyme that produces a staggered cut in double stranded DNA has produced a…?
sticky end cut
The process of introducing recombinant DNA into a plasmid is called:
cloning
In PCR why is DNA heated to over 95 degrees centigrade
to denature the double stranded DNA
In RNA splicing, an active splicesome is generated when:
u4 disassociates
to get cystic fibrosis one must have
To have cystic fibrosis, an individual must have inherited two faulty alleles from their parents; one from their father and one from their mother.
what are alleles?
Alleles are different forms of a gene.
Neonatal screening is carried out:
after birth
what did Hershey and Chase do?
confirmed that DNA was the biomolecule that carried genetic information
These experiments were to make sure that DNA was the genetic material which had been discovered by the Swiss physicianFriedrich Miescher in his experiments on white blood cells or leukocytes
Hershey and Chase used T2 phage, a bacteriophage, for their experiments. The phage infects a bacterium by attaching to it and injecting its genetic material into it.
They put labels on phage DNA with radioactive Phosphorus-32. They then followed the phages while they infected E. coli. They found that the radioactive element was only in the bacteria, and not in the phage.
In a second experiment, they put labels on the phage protein with radioactive Sulfur-35. After the phage was attached to the bacterium, the radioactive element was found in the phage, but not in the bacteria. This showed them that genetic material which infects the bacteria is DNA.
what are the building blocks of DNA?
5 carbon sugar deoxyribose
what is a nucleoside
a nucleoside is a nucleobase linked to a sugar
what is a nucleotide:?
what three elements does it contain?
- phosphate, nitrogenous base and 5 carbon sugar deoxyribose
Nucleotides form the basic structural unit of nucleic acids such as DNA.
what is Polymerase Chain Reaction and who discovered it?
Kary Mullis
Cycling process of:
Initial Denaturation
Denaturation - cycle 28-40 times between denaturation and extension
Annealing
Extension
Final Extension
in PCR a temperature of 95 degrees
Denaturation – destabilises H bonds
in PCR a temperature of 55-65 degrees
Annealing – specificity of primer to site
in PCR a temperature of 72 degrees
Extension – polymerase requires 3’ binding
what is the forumla for description in population genetics?
Description: Fr(red) = 7/20 = 0.35
(7 red dots and 20 yellow dots, divide the lowest species by the highest species)
what is evolution?
change in allele frequencies
A gene pool will be in equilibrium under the following conditions:
the population is very large • individuals in the population mate randomly • there is no migration into or out of the population • natural selection does not act on any specific genotypes • males and females have the same allele frequencies [vs. individuals are diploid and reproduce sexually] • no mutations occur
what is Beneficence
- Serving the interests and wellbeing of others
- Act in the best interest of the individual
what is Nonmalfeasance
No official misconduct • Do no harm
Do you have any right to royalties from tests devised after researching donated tissues? Do these tissues still belong to you?
legally no
what act protects human materials?
Human Tissue Act 2004, 2006 • Must have INFORMED CONSENT • Removal, storage and use for scheduled purpose Human Tissue Act covers anything containing cells, (organs > urine) Tissues from autopsy and surgery are distinguishe
what is classed as human tissue?
Biological material of human origin and any substance extracted from it, e.g. DNA
what is transcription
Transcription is the process of making an RNA copy of a gene sequence. This copy, called a messenger RNA (mRNA) molecule, leaves the cell nucleus and enters the cytoplasm, where it directs the synthesis of the protein, which it encodes.
he process by which DNA is copied to RNA is called transcription
what is translation
the process of translating the sequence of messenger RNA to a sequence of amino acids during protein synthesis. the ribosome reads the sequence of the mRNA in groups of 3 bases to assemble the protein
what is the central dogma?
solid arrows: transfers that occur in all cells
Dotted arrows: transfers that occur in some cells
DNA -> RNA -> Protein
DNA to RNA through transcription, RNA to Protein through Translation
what percentage of the human geonome is patented and why?
40%
for research, diagnostics tests and drugs
what is PCR used for?
identification purposes
make many copies of an organism’s DNA sequence so a small number of organisms will become large enough to be identified
Taq polymerase starts copying at
DNA primers attached to the end of the desired gene
when do primers annealise DNA
Primers anneal when DNA is cooled, not when heated.
what are the steps of human development in stem cells?
fertilisation
cleavage (The zygote divides (cleaves) into two identical cells.)
blastocyte formation
Gastrulation
Organogenesis
what type of ‘potent is a zygote?
The zygote is totipotent: it can produce all the cell types needed to make a complete human.
what type of ‘potent are blastocytes
Cells of the inner cell mass of blastocytes are pluripotent: they can form all cell types of the human body except tissues which support the embryo, such as the placenta.
The inner cell mass is the source of one type of stem cell, embryonic stem cells.
name some functions of stem cells
Stem cells are cells that can: • Generate more specialised cell types through the process of cell differentiation. • Divide to make identical copies of themselves, a process called self-renewa
what are some possible uses for stem cells?
To provide lab-grown human or animal tissue for identifying new treatments for disease, including new drugs and other substances, rather than using animals. • To produce new human tissue and organs to replace those lost in injury or disease. See box, Organ regeneration. • To repair tissue by stimulating stem cells already in the body. • To use stem cells from patients with inherited genetic diseases (such as cystic fibrosis or some forms of Parkinson’s disease) to study how the disease develops. • To investigate human development. • To better understand diseases like cancer
what type of ‘potent are embryonic stem cells?
pluripotent
what tpye of ‘potent are tissue stem cells?
multipotent
what is STAP and what happened?
ethod of generating pluripotent stem cells by subjecting ordinary cells to certain types of stress, such as the application of a bacterial toxin, submersion in a weak acid, or physical squeezing
research done by Haruko Obokata
all scientists who tried to duplicate her results failed and suspicion arose that Obokata’s results were due to error or fraud.
what are the three main phases of gene transcription
3 main phases:
Initiation, elongation and termination
what controls which genes are transcribed?
Transcription factors (proteins) bind to promoter regions of the DNA
in RNA synthesis what is thymine replaced with
uUracil instead of Thymine
what is the function of the polyAtail
u50 – 100 A residues
uNo template
uProtects against 3’ exonuclease
uAids in transport
what 3 types of point mutation are there
1•. Silent -> The most frequent type of mutation, doesnt change the amino acid
•
•2. Non-sense -> Changes an amino acid codon into a Stop codon:
•
•3. Mis-sense ->
•Changes one amino acid codon into another amino acid codon.
•
•Changes the primary structure of the protein.
•
which two nucleotides are purine?
Adenine and Guanine
what requirements must be met for random genetic drift?
PHENOTYPIC VARIATION , Inheritance, Random Sampling
what is DNA Polymorphism
DNA polymorphism is any difference in the nucleotide sequence between individuals.
e.g.
single base pair changes, deletions, insertions, or changes in the number of copies of a DNA sequence.
which DNA nucleotide contains adenine?
deoxyadosine 4 monophospahte (dAMP)
what is this?
nucleotide
which two nucleotides are pyramidine?
cytosine and thymine
who was Erwin Chargaff?
he thought compositions of DNA were different between species but consistant within all cells of an organism
Chargaff discovered tworules that helped lead to the discovery of the double helix structure of DNA.
The first rule was that in DNA the number of guanine units equals the number of cytosine units, and the number of adenine units equals the number of thymine units. This hinted at the base pair makeup of DNA.
The second rule was that the relative amounts of guanine, cytosine, adenine and thymine bases varies from one species to another. This hinted that DNA rather than protein could be the genetic material.
what are chargaffs rules?
Amount of A = Amount of T
Amount of C = Amount of G
Amount of Purine = Amount of Pyramidine
Chargaff discovered tworules that helped lead to the discovery of the double helix structure of DNA.
The first rule was that in DNA the number of guanine units equals the number of cytosine units, and the number of adenine units equals the number of thymine units. This hinted at the base pair makeup of DNA.
The second rule was that the relative amounts of guanine, cytosine, adenine and thymine bases varies from one species to another. This hinted that DNA rather than protein could be the genetic material.
who was rosalind franklin
lead to the discorvery of the double dna helix
she discovered dna has a helical structure and was working on the structure of dna
who were watson and crick
discovery of the molecular structure of DNA based on all its known features - the double helix
DNA is composed of 2
chains of nucleotides that
form a double helix
shape.
The two strands are
antiparallel. (C5’ to C3’)
The backbone of the DNA
molecule is composed of
alternating phosphate
groups and sugars.
The complimentary
nitrogenous bases form
hydrogen bonds between
the strands.
A is complimentary to T
and G is complimentary
to C.
Turn in helix is 34Å and
10bp
B form of DNA –
right handed helix
Major and Minor Groves
how do we read DNA structures?
5’ - 3’
and backwards too for double stranded 3’ - 5’
what is A complimentary to
T
what are 3 alternative DNA structures
B DNA -> vast majority of dna in this form
A DNA -> forms in low humidity, 11 base pairs per turn, forms in certain DNA - protein complexes, central hole (RNA - RNA + RNA - DNA)
Z DNA -> left hand helix zig zag appearance
what is G complimantary to
C
what are exons?
sound in mrna -> code for protein product
first and last exons contain untranslated regions (UTRs)
5’ exon ocontains initiator codon
3’ codon contains termination codon
what is RNA
contains ribose not deoxyribose
uracil not thymine
mainly single stranded, can be double stranded by complimentary base pairing
protein coding genes are
mRNA - > carries messages to ribosomes from DNA
what is epigenetics?
“On top of or in addition to genetics”
“Heritable, but potentially reversible, changes in gene expression that occur without changes in the DNA sequence”
May change over the lifetime of an individual
Influenced by environment, especially in development -
what are epigenetic marks and what do they do?
epigenetic marks tell your genes to switch on or off
Through epigenetic marks, environmental factors like diet, stress and prenatal nutrition can make an imprint on genes passed from one generation to the next.
what is dna ligase
An enzyme DNA ligase is the a glue that joins the ends of the recombinant DNA and plasmid together
what is primase
DNA primase is an enzyme involved in the replication of DNA. DNAprimase is a type of RNA polymerase which creates a RNA primer (later this RNA piece is removed by a 5’ to 3’ exonuclease); next, DNA polymerase uses the RNA primer to replicate ssDNA.
Primase is an enzyme that synthesizes short RNA sequences called primers. These primers serve as a starting point for DNA synthesis. Since primase produces RNA molecules, the enzyme is a type of RNA polymerase. Primase functions by synthesizing short RNA sequences that are complementary to a single-stranded piece of DNA, which serves as its template. It is critical that primers are synthesized by primase before DNA replication can occur. This is because the enzymes that synthesize DNA, which are called DNA polymerases, can only attach new DNA nucleotides to an existing strand of nucleotides. Therefore, primase serves to prime and lay a foundation for DNA synthesis.
what is DNA replication?
DNA replication is the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules. Replication is an essential process because, whenever a cell divides, the two new daughter cells must contain the same genetic information, or DNA, as the parent cell.
what is an enzyme?
A macromolecule, usually a protein, that catalyzes biochemical reactions, lowering the activation energy and increasing the rate of reaction.
what is a transcription factor?
proteins involved in the process of converting, or transcribing, DNA into RNA
what are promotor sequences?
Promoter sequences are DNA sequences that define where transcription of a gene by RNA polymerase begins. Promoter sequences are typically located directly upstream or at the 5’ end of the transcription initiation site. RNA polymerase and the necessary transcription factors bind to the promoter sequence and initiate transcription. Promoter sequences define the direction of transcription and indicate which DNA strand will be transcribed; this strand is known as the sense strand.
Many eukaryotic genes have a conserved promoter sequence called the TATA box, located 25 to 35 base pairs upstream of the transcription start site. Transcription factors bind to the TATA box and initiate the formation of the RNA polymerase transcription complex, which promotes transcription.
what is a TATA box
A TATA box is a DNA sequence that indicates where a genetic sequence can be read and decoded. It is a type of promoter sequence, which specifies to other molecules where transcription begins. Transcription is a process that produces an RNA molecule from a DNA sequence. The TATA box is named for its conserved DNA sequence, which is most commonly TATAAA. Many eukaryotic genes have a conserved TATA box located 25-35 base pairs before the transcription start site of a gene. The TATA box is able to define the direction of transcription and also indicates the DNA strand to be read. Proteins called transcription factors can bind to the TATA box and recruit an enzyme called RNA polymerase, which synthesizes RNA from DNA.
what is ATP
Adenosine 5’-triphosphate, or ATP, is the principal molecule for storing and transferring energy in cells. It is often referred to as the energy currency of the cell and can be compared to storing money in a bank. ATP can be used to store energy for future reactions or be withdrawn to pay for reactions when energy is required by the cell. Animals store the energy obtained from the breakdown of food as ATP. Likewise, plants capture and store the energy they derive from light during photosynthesis in ATP molecules. ATP is a nucleotide consisting of an adenine base attached to a ribose sugar, which is attached to three phosphate groups. These three phosphate groups are linked to one another by two high-energy bonds called phosphoanhydride bonds. When one phosphate group is removed by breaking a phosphoanhydride bond in a process called hydrolysis, energy is released, and ATP is converted to adenosine diphosphate (ADP)
what is RNA polymerase?
RNA polymerase is an enzyme that is responsible for copying a DNA sequence into an RNA sequence, duyring the process of transcription. As complex molecule composed of protein subunits, RNA polymerase controls the process of transcription, during which the information stored in a molecule of DNA is copied into a new molecule of messenger RNA.
RNA polymerases have been found in all species, but the number and composition of these proteins vary across taxa. For instance, bacteria contain a single type of RNA polymerase, while eukaryotes (multicellular organisms and yeasts) contain three distinct types. In spite of these differences, there are striking similarities among transcriptional mechanisms. For example, all species require a mechanism by which transcription can be regulated in order to achieve spatial and temporal changes in gene expression.
what is phenotypic plasticity?
when an organism activates different phenotypes in response to its environment
A highly illustrative example of phenotypic plasticity is found in the social insects, colonies of which depend on the division of their members into distinct castes, such as workers and guards.These two castes differ dramatically in appearance and behaviour. However, while these differences are genetic in basis, they are not inherited; they arise during development and depend on the manner of treatment of the eggs by the queen and the workers, who manipulate such factors as embryonic diet and incubation temperature. The genome of each individual contains all the instructions needed to develop into any one of several ‘morphs’, but only the genes that form part of one developmental program are activated.
what are the two forms of genetic information in a cell?
genetic and epigenetic
Genetic information:
The building block for the manufacture of ALL proteins in the body
Epigenetic information:
How, when and where this genetic information should be used
what is gene transcription?
The process of making RNA from DNA
RNA polymerases
Portion of DNA copied = Template
Resulting RNA molecule = Transcript
what are the three main processes of gene transcription?
Initiation, elongation and termination
what is keinfelters?
xxy (male as only males have y chromosones)
genetic condition but it is not ‘inherited’ from your parents. It usually happens randomly during meiosis - cell division that produces egg and sperm cells
lives till adulthood (normal life span)
treatment: testosterone replacement, gynaecomastia treatement, infertility treatment
how do you correctly read PCR results?
the top is negative (lowest number) and the bottom is positive (highest number). the fragments (lines) are pushed from top to bottom and those that are the smallest move the furthest from the top and the fragments that are the largest wont move as far from the negative end.
the numbers go from highest at the top (negative) to lowest at the bottom (positive)
agarose gel is used for larger base pairs and SDS page is used for smaller base pairs
uses an electical charge to push the fragments down the gel
label this diagram
uses an electrical current
DNA is negatively charged so it goes to the cathode
what are the two equations for the hardy weinburg principle?
p2+2pq+q2=1
p+q=1
what is a prenatal test and what are the results of taking one?
a harmless test to determine birth defects before the baby is born
used to help calculate the odds that the fetus might be born with genetic disorders, such as Down syndrome, cystic fibrosis, Tay-Sachs disease, or sickle cell anemia.
risk of miscarriage
label the bonds in this diagram
what is an autosomal dominant condition?
•an abnormality occurs when only one of the genes from one parent is abnormal
The alteration is located on an autosome.
people with the condition in each generation
males and females affected in roughly equal proportions
all forms of transmission present (male to female, male to male, female to male and female to female).
At conception, each child has a 1 in 2 (50%) chance of inheriting the condition.
Examples of autosomal dominant conditions include:
Huntington disease
Achondroplasia
Marfan syndrome
loeys dietz syndrome
what is an autosomal recessive condition?
condition that appears only in individuals who have received two copies of an altered gene, once copy from each parent. People with two copies of the altered gene are called homozygotes. Their parents, each with a single copy of the altered gene, appear normal and are called heterozygotes or carriers of the altered gene.
In autosomal recessive inheritance, people with one copy of the gene alteration do not have the condition. They are said to be carriers for the autosomal recessive condition.
males and females have the condition in roughly equal proportions
people with the condition are usually in one sibship in one generation
At conception each child of parents who are both carriers has a 1 in 4 (25%) chance of being an unaffected non-carrier; a 2 in 4 (50%) chance of being a carrier and a 1 in 4 (25%) chance of inheriting the condition.
Examples of autosomal recessive conditions include:
cystic fibrosis
sickle-cell anaemia
MCADD
PKU Phenylketonurea
beta-thalassaemia.
what is an x linked recessive condition?
condition in which an alteration in one gene on the X chromosome causes the condition in males but not usually when females have one copy of the altered gene.
can only be passed from the mother to son as fathers only pass on their y chromosone to the son
males affected almost exclusively
the gene alteration can be transmitted from female carriers to sons
affected males cannot transmit the condition to their sons.
conditions:
haemophilia (factor 8 or 9 defective)
colour blindness
Duchenne muscular dystrophy.
what is an x linked dominant condition?
The sons of a man with an X-linked dominant disorder will all be unaffected (since they receive their father’s Y chromosome), and his daughters will all inherit the condition. A woman with an X-linked dominant disorder has a 50% chance of having an affected fetus with each pregnancy
conditions:
chondrodysplasia punctata (short stature)
rickets
kleinefelter syndrome
Rett syndrome, incontinentia pigmenti type 2, and Aicardi syndrome
what is a Y linked condition
caused by mutations on the Y chromosone
Y-linked disorders in humans can only be passed from men to their sons; females can never be affected because they do not possess Y allosomes.
azoospermia
hairy ear pinnae
retinitis pigmentosia
y chromosone infertility
what is mitochrondial linked condition
also known as maternal inheritance, applies to genes in mitochondrial DNA. Because only egg cells contribute mitochondria to the developing embryo, only mothers can pass on mitochondrial conditions to their children. An example of this type of disorder is Leber’s hereditary optic neuropathy.
an organism with two different alleles for a trait is considered…
An organism that has two different alleles for a single trait is said to be heterozygousfor that trait
what generation letter did mendel refer to as the parental generation between two true breeding plants
Mendel referred to the parental generation in the cross pollination between two true-breeding plants as the P generation.
what letter did mendel give to the offspring of the cross breeding parental generation of two true breeding plants
F1
In the cross-pollination between a true-breeding yellow pod plant and a true-breeding green pod plant, where green pod color is dominant, the resulting offspring (F1 generation) will be…
In the cross-pollination between a true-breeding yellow pod plant(gg) and a true-breeding green pod plant(GG), where green pod color is dominant, the resulting offspring (F1 generation) will be all green. The genotype of the F1 plants is (Gg).
If the green F1 plants from the green dominant, yellow recessive parental generation allowed to self-pollinate, the resulting offspring (F2 generation) will be…
If the green F1 plants from the green dominant, yellow recessive parental generation are allowed to self-pollinate, the resulting offspring (F2 generation) will be 1/4 yellow and 3/4 green.
In a cross between a green F1 plant from the previous example and another green pod colored plant with an unknown genotype, the resulting offspring (F2 generation) were all green. What is the genotype of the unknown plant?
the genotype of the unknown plant is GG
In a dihybrid cross, the expected ratio in the F2 generation is..
9:3:3:1
The idea that different pairs of alleles are passed to offspring independently is Mendel’s principle of:
independant assortment
the genes that determine a trait assort independently of the genes for other traits. As a result, new combinations of genes, present in neither parent, are possible.
The idea that for any particular trait, the pair of alleles of each parent separate and only one allele from each parent passes to an offspring is Mendel’s principle of
segregation
genes occur in pairs and during the process of sex cell production, the members of each pair separate so that each sperm and ovum cell receives one member of each pair.
what 3 codons are stop codons?
DNA stop codons
TAG, TAA, TGA
or replace T with U for RNA
UAA, UAG, or UGA to signify the end of protein synthesis
what is the function of AUG codon
AUG serves two related functions:
start signal for translation
it codes for the incorporation of the amino acid methionine (Met) into the growing polypeptide chain
how are traits passed from parent to offspring?
gene transmission
If two people who are both carriers for a genetically inherited fatal recessive disease decide to become parents, what will be the odds that their children will also be carriers?
If a woman is homozygous normal and her husband is heterozygous for a genetically inherited recessive disease and they decide to become parents, what is the probability that they will have a healthy child?
All of the children will be healthy since none of them can be homozygous recessive (aa). However, there will be a 50% chance at each birth that the children will be carriers (Aa). The remaining 50% will be homozygous dominant (AA).
describe a glycosidic bond
The nitrogen bases are pyrimidine in structure and form a bond between their 1’ nitrogen and the 1’ -OH group of the deoxyribose.
what is this?
adenine
it can also have two ‘NH’s split off at the top instead of NH2
Its chemical formula is C5H5N5 (count the number of C’s etc that appear on the structure when figuring out which nucleotide the question is showing)
what is this?
Guanine neucleotide
purine, (double-ring bases) nitrogeous base
what are double-ring bases called?
purines
what are single ringed bases called?
pyramidines
what is primase?
an enzyme that synthesizes short RNA sequences (primers). it is a type of RNA polymerase
what is polymorphism?
Genetic polymorphism promotes diversity within a population. It often persists over many generations because no single form has an overall advantage or disadvantage over the others regarding natural selection. A common example is the different allelic forms that give rise to different blood types in humans.
•DNA level variation.
•
•Protein level variation.
•
Morphological variation
what is the connection between morphological and molecular evolution?
- Single-gene traits.
- Polygenic traits.
what is a single gene trait?
•Different variants (alleles) of a single gene
what is a polymorphic trait?
•Different variants (alleles) of several genes
what does a dominant allele determine
Dominant allele: Allele that determines the phenotype in a heterozygous condition
what does a recessive allele determine?
•Recessive allele: Displays no influence on the phenotype in heterozygous individuals.
in mendalin genetics which part of the punnet square is homologous?
AA and aa because they must be the same
in mendalin genetics which part of the punnet square is heterozygous?
Aa and aA because heterzygous means different
what are 3 examples of single gene traits?
tongue rolling, widows peak and attached earlobes
what does phenotypic variation result from?
•Phenotypic variation results from environmental influences on the genotype.
is this an example of phenotypic or genotypic variation?
phenotypic
because their appearance depends on the differing environments whereas if it was genotypic the non windy plant would stay the same when transferred to the windy site and the windy plant would stay the same when transferred to the non windy site
is this an example of phenotypic or genotypic variation?
phenotypic
the height of the plant depends on its environment (altitude in this case), if it was genotypic the plant would stay the same height regardless of altitude or environment
what is phenotypic variation?
•Phenotypic variation results from environmental influences on the genotype.
•
•Phenotypic variation has both environmental and genotypic components.
•
If the genotypes are identical then any variation must result from environmental influences
what is mendalins law of inheritance?
Populations could be described genetically in terms of their phenotype frequencies, genotype frequencies, and allele frequencies
his three laws of inheritance are:
- the Law of Dominance
- the Law of Segregation
- the Law of Independent Assortment
Which cross would best illustrate Mendel’s Law of Segregation?
A. TT x tt
B. Hh x hh
C. Bb x Bb
D. rr x rr
Bb x Bb - both parent show dominant trait, but some recessive offspring will be produced (each parent carries a “b”)
what is evolution in genetics terms?
•Evolution is simply a change in frequencies of alleles in the gene pool of a population.
e.g. parent 92% A and 8% a
offspring become 90% A and 10% a
•evolution has occurred between the generations.
•
•The entire population’s gene pool has evolved in the direction of a higher frequency of the a allele. It was not just those individuals who inherited the a allele that evolved.
What would be the percentages of genotypes & phenotypes if one of the white F1 plants is crossed with a pink-flowered plant?
do a punnet square!
remember f1 is two purebred plants crossed so white is the dominant from that crossing so would be Ww and pink would be ww
50% heterozygous white & 50% homozygous recessive pink
what is the hardy weinberg principle?
•Godfrey Hardy (an English mathematician) and Wilhelm Weinberg (a German physician).
•
•Showed in 1908 that the frequency of homozygotes and heterozygotes in a population’s gene pool stays constant from generation to generation if certain conditions were fulfilled.
what conditions must be fufilled if the hardy weinberg equilibrium is to remain constant within a population
•Evolution will not occur in a population if seven conditions are met:
•
•1. Mutation is not occurring.
•2. Natural selection is not occurring.
•3. The population is infinitely large.
•4. All members of the population breed.
•5. All mating is totally random.
•6. Everyone produces same number of offspring.
7. There is no migration in or out of the population
is it likely or unlikely for the 7 conditions of the hardy weinberg principle to be fufilled?
unlikely, evolution is inevitable
what are the 5 evolutionary driving forces
•Mutation
•
•Migration
•
•Selection
•
•Mating system
•
•Population size [Genetic drift]
what is the hardy weingberg equilibrium equation used for and what are the two equations
•used to discover the probable genotype frequencies in a population and to track their changes from one generation to another.
p² + 2pq + q² = 1
•p + q = 1
in the hardy weinberg equilibrium equation what does P and Q stand for?
what is the equation p² + 2pq + q² = 1 used to find?
p is the frequency of the dominant allele.
P2 = AA, Pq = Aa (dominant)
q is the frequency of the recessive allele
qq = aa (recessive)
•For a trait controlled by a pair of autosomal alleles (A and a):
how do you work out the hardy weinberg equation?
p2 = p squared
2pq = 2 x p x q
what is mendals law of dominance?
In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation (the dominant trait). Offspring that are hybrid for a trait will have only the dominant trait in the phenotype.
what does hardy weinbergs equilibrium not allow for?
immigration, emmigration, births and deaths
which equations are also correct for the hardy weinberg principle equation p + q = 1?
p = 1 - q
q = 1 - p
what did hardy and weinberg discover with their equilibrium?
•chances of all possible combinations of alleles occurring randomly is:
(p + q)² = 1
Or, more simply:
pp + pq +qp + qq = 1
p² + 2pq + q² = 1
what is p² in the hardy weinberg principle equilibrium equation?
the predicted frequency of homozygous dominant (AA) individuals in the population,
what is 2pq in the hardy weinberg equilibrium equation?
the predicted frequency of heterozygous (Aa) individuals
what is q² in the hardy weinberg equilibrium equation
the predicted frequency of homozygous recessive (aa) individuals
when observing phenotypes what is it only possible to know in the hardy weinberg equilibrium
•It is usually only possible to know the frequency of homozygous recessive individuals.•q² in the Hardy-Weinberg Equation Since they do not have the dominant trait
what can the hardy weinberg principle be used to find out?
it CAN be used to find out whether evolution has occured between generations
•the Hardy-Weinberg equation CANNOT determine which of the various possible causes of evolution were responsible for the changes in allele frequencies in the gene pool.
what is the flow of information?
one way only
DNA ->transcription -> RNA -> Translation -> Protein
what is population genetics?
the study of how genes behave in populations
it involves descriptions and predictions
what is the rule of probability in hardy weinberg genetics?
the probability of randomly encountering an item of a certain type is equal to the frequency of that type in the population
the probability of rolling a 6 on a single die is 1/6
what is B DNA?
vast majority of DNA in this form
helix makes a turn every 3.4 nm
20 base pairs per turn
major groove and the minor groove, which may facilitate binding with specific proteins.
what is A dNA
forms in low humidity
11 base pairs per turn
forms in certain DNA protein complexes
central hole
(RNA - RNA + RNA - DNA)
what is Z DNA?
left hand helix
zig zag appearance
One turn spans 4.6 nm, comprising 12 base pairs
what is this?
B DNA
what is this?
B DNA
what is this?
A DNA
what is this?
A DNA
what is this?
Z DNA
what is this?
Z DNA
what is bioinformatics?
it is a combination of molecular biology, maths and computer science in order to understand the biological significance of a variety of data
why is bioinformatics important?
many uses in forensic and biological sciences
label this, what is it
central dogma
dash lines = special
solid lines = general
All organisms are very similar at the biochemical and molecular level; therefore?
Studies in one organism have wider relevance
describe the central dogma
the central dogma of molecular biology describes the flow of genetic information in cells from DNA to messenger RNA (mRNA) to protein. It states that genes specify the sequence of mRNA molecules, which in turn specify the sequence of proteins
what is the monohybrid ratio?
3:1
its the hybrid of 1 set of traits from p generation to f1 generation
define locus
•Locus = site of allele on chromosome
•Alleles are usually dominant or recessive with respect to their interaction and expression. But can show ?
co dominance or incomplete dominance
what is this an example of?
incomplete dominance
if R+R- creates roan coaws, R+R+ creates red cows and R-R- creates white cows
what is the result?
1 red cow, 2 roan cows, 1 white cow (phenotype)
1:2:1 (genotype)
modified monohybrid
how do we know 9:3:3:1 is the correct ratio for dihybrid crosses?
use a punnet square
what is linkage?
genes close together on a chromosone show linkage
•They tend to enter gametes in parental combinations
•The close together, the stronger the linkage.
•Recombination requires breaking of linkage as a result of crossing over during meiosis
The closer the genes, the less chance of crossover occurring between them
what is this an example of?
double heterozygote
single gene defects can be
•Autosomal dominant
•Autosomal recessive.
•Sex linked dominant
Sex linked recessive
what disorder is this?
autosomal dominant
1:1
1 affected 1 unaffected (50% chance)
what is huntingtons characterised by?
- Caused by stutter on DNA.
- Excessive number of repeats of CAG on
chromosome 4.
- Brain deteriorates in middle age.•If the parent has the disorder, the baby has a 50 percent chance of inheriting it.
- 12 in 100,000 approx.
autosomal dominant
what is Achondroplasia characterised by?
dwarfism, autosomal dominant
Defect on chromosome 4.
Fault in fibroblast growth factor receptor.
80% patients due to new mutation.
More likely if father over 35. 1/25,000
•imperfect bone development causing dwarfism
what is marfan syndrome characterised by?
aracnodactyle hands
Defect on chromosome 15, connective tissue disorder.
causing long limbs and heart defects
dilation of aorta (aorta stretches and weakens)
pectus excavatum (hollow point in ribcage)
marfan syndrome has no cure, but treatments can help delay or prevent complications. Treatments include medicines, surgery, and other therapies.
what is Loeys-Dietz
autosomal dominant
similar to marfan syndrome
High risk of sudden death due to rupture of aortic aneurysm.
Joint hypermobility
Club foot
Curved spine
no cure, medications and surgery
what is this an example of?
autosomal dominant
polled = no horns
what disorder is this?
autosomal recessive
1 affected, 2 carriers, 1 unaffected
3 normal : 1 sufferer Phenotypes
what is this an example of?
autosomal recessive
what is this an example of?
autosomal recessive
hairlessness in animals
describe cystic fibrosis
autosomal recessive
•Caused by deletion on chromosome 7 (in most cases)
•Failure of Chloride (Cl-) ion transport.
•1 in 1,800 white people.
•An abnormality only occurs when both chromosomes carry abnormal genes.
•If both parents are carriers, a baby has a 25 percent chance of having the disorder.
Failure of Cl- ion transport at cell surface causes:-
Lungs – thick bronchial secretions block the small airways causing inflammation
Liver – thick secretions (TS) block bile duct
Pancreas - TS may block gland completely
Small intestine – meconium ileus
Reproductive organs – infertility
Sweat and salivary glands - secrete fluid with more salt than normal
describe pku - Phenylketonurea
chromosone 12
Defective enzyme prevents conversion of phenylalanine to tyrosine.
Too much phenylalanine, too little tyrosine.
Brain/nervous system fails to develop normally
1/12,000 Caucasian births.
Controlled by careful diet soon after birth.
where is the homologous and differential regions on the x and y chromosomes?
homologous at bottom, differential at top
describe x linked conditions
•Disorder determined by genes on the X chromosome
•Affects mainly males, have no spare copy
•Sons of women who are carriers each have a one in two chance of having the disorder.
•Daughters of women who are carriers have a one in two chance of being a carrier.
Men with the disorder pass the gene on to all their daughters who become carriers. (Provided that the disorder is not fatal during infancy. Eg colour blindness not fatal
describe Duchene muscular dystrophy
- Progressive muscle weakening.
- Due to abnormal muscle protein.
1 in 3,500 males.
Onset 3 – 5 years
Also cardiomyopathy,
mental disability
Death 15 – 25 years
what are Multifactorial problems
give examples
•Some birth defects do not follow a single gene or chromosomal abnormality pattern
•
•They may be due to several problems, or a combined effect of genes and the environment
•
•It is difficult to predict inheritance of abnormalities caused by multiple factors
•
examples:
- heart defects,
- cleft lip or cleft palate,
- and neural tube defects
how are genetics problems diagnosed?
•Family tree
•Screening parent’s DNA
•Prenatal testing:
•chorionic villus sampling
•amniocentesis
•
Pure breeding red flowered antirrhinums were crossed with pure breeding white flowered antirrhinums and the F1 progeny were all pink flowered.
The F1 were crossed to produce the F2. One hundred F2 plants were counted and were found to have the following phenotypes:-
20 Red Flowered
53 Pink Flowered
27 White Flowered.
Interpret these results.
An inherited condition of chickens causes their legs to be stunted.
Hence they are called ‘creeper chickens’.
When two creeper chickens are crossed the resultant offspring are either normal or creeper, with twice as many ‘creepers’ being produced than normal birds.
Explain these results.
This problem is explained because the creeper allele is lethal in the homozygous condition and fails to develop and so is not seen. The creeper condition is caused when the individual is a heterozygote (with one normal and one creeper allele).
what is this?
turners syndrome XO
what must there be for evolution to occur?
For evolution to occur there must be polymorphism (variation) present in the population
how many types of mutation are there?
•Point mutation:•1. Silent
•
•2. Non-sense
•
•3. Mis-sense
what is silent mutation?
•The most frequent type of mutation.
•
•Mainly at third codon positions.
•
•Genetic code is redundant.
•
•Does not change the amino acid.
what is non sense mutation
•Changes an amino acid codon into a Stop codon:
•
•UAA
•UAG
•UGA
what is a missense mutation
•Changes one amino acid codon into another amino acid codon.
•
•Changes the primary structure of the protein.
•
•Knock-on effects on the secondary, tertiary, and quaternary structure too:
•
•Depending on the change in size and shape;
•
•Depending on the change in charge or polarity.
what are the other reasons for intersex conditions
•Abnormal differentiation of gonads
•
•Phenotypic sex ambiguous or not in agreement with chromosomal sex, hermaphrodites
Abnormalities which cause an increase in androgen and testosterone synthesis may confer a competitive advantage. Eg. Congenital Adrenal Hyperplasia
what is mosaicism
•presence of two or more chromosome patterns in the cells of a person, resulting in two or more cell lines (i.e., in humans some with 46 chromosomes, others with 47)
what is this an example of?
nonsense mutation, causes stop codons with mutations
what is this an example of?
missense mutation,
name 3 amino acids with positively charged side chains
arginine, histidine, lysine
name 2 amino acids with negatively charged side chains
aspartic acid
gluatamate acid
name 4 amino acids with polar but uncharged side chains
serine, threonine, glutamine, asparagine
name 3 special cased for amino acids
proline, cysteine, glycine
name 8 amino acids with hydrophobic side chains
alanine, valine, isoleucine, leucine, methionine, tryptophan, tyrosine, phenylalanine
what is the amino acid structure?
what is this?
glycine
amino acid
what is this?
alanine amino acid
what is this?
valine amino acid
what is this?
leucine, amino acid
what is this?
isoleucine amino acid
what model of dna replication is this
semi conservative model
what model of DNA replication is this?
conservative model
what model of dna replication is this?
the dispersive model
what was the Meselson-Stahl experiment?
they proved watson and cricks theory of dna being semi conservative,
who was Kornberg and what did he do?
Identified all the components needed to replicate E.coli DNA in vitro he found the enzyme that assembles the building blocks into DNA, named DNA polymerase. This ubiquitous class of enzymes make genetically precise DNA and are essential in the replication, repair and rearrangements of DNA.
what are the key components of replication?
uA DNA template
uMagnesium ions
Enzyme – DNA polymerase III (Prokaryotes
all 4 dntps - Deoxyribonucleotide triphosphate, referring to the four deoxyribonucleotides: dATP, dCTP, dGTP and dTTP. A for adenine, C for cytosine, G for guanine and T for Thymine.
what is dna polymerase
Formation of a phosphodiester bond
Between 3’OH of Deoxyribose on last nucleotide and 5’phosphate of dNTP
uFinds correct dNTP
ONLY synthesis 5’ to 3’
DNA polymerases are the enzymes that replicate DNA in living cells. They do this by adding individual nucleotides to the 3-prime hydroxl group of a strand of DNA. The process uses acomplementary, single strand of DNA as a template.
This enzyme adds nucleotides to an existing strand
what is a rep fork?
During DNA* replication a DNA double helix must unwind and separate so that DNA polymerase enzymes can use each single strand as a template for the synthesis of a new double strand. Strand separation is catalyzed by a Helicase enzyme. A number of helper proteins prevent the strands from coming back together before replication is complete. Partial separation of the double helix forms a replication fork*.
what is replication origin?
The origin of replication (also called the replication origin) is a particular sequence in a genome at which replication is initiated.[1] This can either involve the replication of DNA in living organisms such as prokaryotes and eukaryotes, or that of DNA or RNA in viruses, such as double-stranded RNA viruses.
what is a replication initiator protein
Proteins that catalyze the unwinding of duplex DNA during replication by binding cooperatively to single-stranded regions of DNA or to short regions of duplex DNA that are undergoing transient opening. In addition DNA helicases are DNA-dependent ATPases that harness the free energy of ATP hydrolysis to translocate of DNA strands.
what is primosome?
a primosome is a protein complex responsible for creating RNA primers on single stranded DNA during DNA replication.
what is semi discontinuous replication?
uSingle stranded binding proteins
u
uDNA Pol III only 5’ à 3’
u
uLeading and Lagging strands
DNA synthesis at a replication fork of a replication bubble is semidiscontinuous
what is a replication bubble
A portion of the DNA molecule that has opened, providing a site for two replication forks.
define DNA replication
The copying of DNA to pass on information
what are osaki fragments
The noncontinuous segments of newly synthesized DNA along the lagging strand
Define transcription
The process of copying the genetic code from DNA into the form of mRNA which then leaves the cell neucleus and enters the cytoplasm where it directs the synthesis of protein
define promotor
A sequence of DNA nucleotides that signals where transcription will begin and where RNA polymerase binds
enables transcription of the gene.
how is RNA different from DNA
. RNA is single-stranded, not double stranded
- The five-carbon sugar is ribose instead of deoxyribose
- The nitrogenous base uracil replaces the DNA base thymine
define lagging strand
During replication, the DNA strand that grows discontinuously and in the direction opposite of the replication fork.
define leading strand
During replication, the strand of DNA that is synthesized continuously in the direction of the replication fork.
Define the role of topoisomerase
This enzyme cuts and rejoins the helix
define ligase
This enzyme brings together the Okazaki fragments
define the role of helicase
This enzyme unwinds our double helix into two strands
what is dispersive replication
A proposed mechanism of DNA replication, suggesting that segments of both parental strands act as templates for a new strand. The resulting daughter strands contain a mixture of old and newly synthesized DNA.
what is semi conservative replication
A model (born out by experimental evidence) for DNA replication in which each DNA strand acts as a template for the synthesis of a new complementary strand.
define conservative replication
A proposed mechanism for DNA replication that suggested replication resulted in a DNA molecule consisting of two new, and no parental, strands. The mechanism has been disproven.
A-T and T-A requires how many H-bonds?
2
C-G and G-C requires how many H-bonds
3
define the role of hydrogen bonds in DNA
This type of bond holds together the two DNA strands by linking complementary nitrogenous bases; this contributes to DNA’s secondary structure, a double helix
Define phosphodiester bonds
Bonds that link nucleotides of a DNA strand together. The 3′ and 5′ carbons of sugars of two respective nucleotide subunits are linked together, and the phosphate group of the bottom nucleotide lies in between.
what happens during initiation - DNA replication?
RNA primer made by DNA primase starts replication of lagging strand (synthesis of 1st osaki fragment)
what is circular dna?
uMany circular DNA molecules remain so during replication
u
uAs strands uncoil severe tension upahead
u
uTopoisomerases introduce negative supercoils
A nucleic acid that carries the genetic information in cells and some viruses, consisting of two long chains ofnucleotides twisted into a double helix and joined by hydrogen bonds between the complementary bases adenine andthymine or cytosine and guanine. DNA sequences are replicated by the cell prior to cell division and may include genes,intergenic spacers, and regions that bind to regulatory proteins.
label the diagram
what is dna cloning?
provide multiple copies of DNA for future experiments.
•To investigate DNA/RNA/protein requires a large quantity of the nucleic acid/protein so as to perform numerous molecular biology experiments
how is DNA cloned?
DNa is isolated then inserted into a plasmid (bacterial DNA) in a process called cloning
- The introduction of this ‘foreign’ DNA into the bacterial plasmid DNA will enable hundreds of copies of the ‘foreign’ DNA to be produced
- The cloning of an organisms DNA with the plasmid produces Recombinant DNA
- Once this recombinant DNA has been produced this can be study extensively in the lab
what is recombiant DNA?
•Recombinant DNA is made by cutting a DNA fragment out of one place and inserting it into another
- The ‘foreign’ (donor) DNA fragment is ‘spliced’ into a specific location in the ‘host’ DNA of the plasmid
- The plasmid (containing the recombinant DNA) can then be added to a bacterial cell
- Every time the bacteria copies its own DNA it will also copy the plasmid (recombinant DNA)
what is Restriction Endonucleases
- commonly known as ‘restriction enzymes’
- Restriction endonucleases cut double stranded DNA at specific target sites
- Able to cut through the DNA’s phosphate backbone
•Restriction enzymes recognise palindromic sequences
what are Palindromic sequences
•Palindromic = both strands have same nucleotides sequence but in anti-parallel orientation
e.g.
5’ GAATTC 3’
3’ CTTAAG 5’
restriction endonucleases can produce what kinds of ends/cuts?
•restriction Enzyme can produce either sticky (staggered cut) or blunt (even cut) ends
what cut is this an example of?
blunt end cut
what type of cut is this and example of?
staggered end cut
how do plasmids occur?
plasmids are derived from a natural plasmid found in bacteria/virus
•Plasmids occur naturally:
stable genetic elements found in
bacteria, fungi and mitochondria of
some plants
•
•Natural plasmids are used by
micro-organisms to enable survival
e.g make bacteria antibiotic resistant
how do plasmids replicate?
autonomously
- Plasmids exist and replicate independently (replicate autonomously) of the bacteria cells chromosome
- When ever the bacteria replicates its own bacterial DNA, it will also replicate the plasmid DNA
label this
what have dna plasmids been modified by scientists to be able to do?
•enable DNA cloning/gene expression of recombinant DNA
- maximum expression of recombinant DNA
- have an area where recombinant DNA can be introduced into the plasmid
- identification of bacteria that contain the plasmid
what is a selection marker
ampicillin
Allows scientists to select for bacteria that has the plasmid
what does a multiple cloning site contain
MCS: contains different restriction sites where different restriction enzymes can cut
The following is the type of experiment using garden peas that Gregor Mendel could have performed in his monastery garden.
It starts with a cross between two different true breeding varieties of pea plants. One variety has seed which is round and yellow, and the other has seed which is green and wrinkled.
The F1 were all round and yellow. When these were crossed to produce the F2 the following phenotypes were found:-
171 round yellow
65 round green
60 wrinkled yellow
24 wrinkled green
If the genes are segregating independently, what would be the expected ratio of phenotypes resulting from a cross between the F1 and the green wrinkled parent
it shows a 9:3::1 ratio where 2 gene pairs are segregating independantly
the f1 x green wrinkled would be:
1 round yellow : 1 round green : 1 wrinkled yellow : 1 wrinkled green
A pure breeding, mildew resistant bean plant with pink seeds was crossed with a
pure breeding, mildew susceptible bean plant with white seeds.
The F1 were all found to have pink seeds and mildew resistance.
When the F1 were backcrossed to the parental plants which had white seeds and
were susceptible to mildew the following plants were produced:-
393 pink seeds, mildew resistant
101 pink seeds, mildew susceptible
89 white seeds, mildew resistant
367 white seeds, mildew susceptible.
Are the genes for seed colour and mildew resistance independently assorted?
If the genes are linked how many map units Cm (centi-morgans) apart are the two
loci?
1:1:1:1
1 pink mildrew resistant
1 pink mildew suseptible
1 white mildew resistant
1 pink mildew suseptible
This problem illustrates linkage, which is when the two alleles are sufficiently close together on the same chromosome to mean that they tend to enter gametes in parental combination. Distances between genes on a chromosome are measured in map units.
F1 backcrossed to parental plants which were doubly recessive (white seeds and susceptible to mildew).
If independent assortment expect a 1 : 1 : 1 : 1 ratio
Total number of bean plants counted in backcross generation = 950.
950/4 = 237.5; if a 1 : 1 : 1 : 1 ratio
Observed
Expected
Pink, Resistant (Parental)
393
237.5
Pink, Susceptible (Recomb)
101
237.5
White, Resistant (Recomb)
89
237.5
White, Susceptible (Parental)
367
237.5
Shows more than expected Parental compared to Recombinants.
Χ2 (chi squared) test to see if the difference between Observed and Expected is significant
Χ2 = (393 – 237.5)2 + (101 – 237.5)2 + (89 – 237.5)2 + (367 – 237.5)2
237.5 237.5 237.5 237.5
= 101.8 + 78.5 + 92.9 + 70.6
= 348.8; 3 degrees of freedom; less than 0.005 probability; reject 1:1:1:1 hypothesis
Percentage Recombinants = Map units (mu) apart of the two loci
= 190/950 x 100 = 20mu apart.
what is Cdna
complementary DNA
complementary DNA (cDNA) is double-stranded DNA synthesized from a messenger RNA (mRNA) template in a reaction catalysed by the enzyme reverse transcriptase. cDNA is often used to clone eukaryotic genes in prokaryotes.
what is mtDNA
Mitochondrial DNA – is passed from mothers to both genders of her children, but only passed on by females. Males carry their mother’s mitochondrial DNA (mtDNA) but they don’t pass it on.
what is Y - line DNA
tests the Y chromosome which is passed from father to son, along, in most cases, with the surname. Only men can test for this, because only men have a Y chromosome,
what does autosomal dna do
tests the rest of the DNA provided by both parents on the 23 chromosomes, not just two direct lines, as with Y-line and mitochondrial DNA.
what is this?
thymine
neucleotide
pyramidine
goes with adanine
what is this?
uracil
takes the place of thymine in RNA and matches with adanine which is a purine
uracil is pyramidine
C4H4N2O2
what are complimentary base pairs?
Two of the five bases in nucleic acids, adenine (2) and guanine (3), arepurines. In DNA, these bases form hydrogen bonds with their complementary pyrimidines thymine and cytosine, respectively. This is called complementary base pairing. In RNA, the complement of adenine is uracil instead of thymine.
what is mendels law of segregation?
segregation of genes occurs during meiosis in eukaryotes, which is a process that produces reproductive cells called gametes.
Mendel’s law of segregation, states that allelepairs separate or segregate during gamete formation, and randomly unite at fertilization.
gene can exist in more than one form.
Organisms inherit two alleles for each trait.
When sex cells are produced (by meiosis), allele pairs separate leaving each cell with a single allele for each trait.
When the two alleles of a pair are different, one is dominant and the other is recessive.
what is mendels law of independant assortment
Mendel’s law of independent assortment, states that allele pairs separate independently during the formation of gametes. This means that traits are transmitted to offspring independently of one another.
Mendel formulated this principle after performing dihybrid crosses between plants that differed in two traits, such as seed color and pod color.
After these plants were allowed to self pollinate, he noticed that the same ratio of 9:3:3:1appeared among the offspring. Mendel concluded that traits are transmitted to offspring independently.
how do you calculate map units in mendalin genetics?
Percentage Recombinants = Map units (mu) apart of the two loci
= 190/950 x 100 = 20mu apart.
parentage recombinants = Pm and mP (heterozygotes)
what are histones?
Histones are globular proteins that, together with the DNA, make up the nucleosome ─ the structural unit of chromatin. Histones influence how tightly or loosely packed the chromatin is during the phase when gene transcription occurs. In this way histones influence whether genes can be transcribed.
HISTONE – Small basic protein bound to DNA
what are the two types of epigenetic mark?
chemical - methylation
protein - histones
label this diagram
chromatin
what is dna methylation
a methyl group is covalently added to the fifth carbon of the cytosine ring to form 5-methyl cytosine.
DNA methylation occurs predominately on the CpG islands. DNA methylation is actively involved in regulating
cell differentiation and function. When too much or too little
methylation occurs, it can often negate a gene’s function and thus causes unwanted alterations in the cell and even result in diseases.
methylation of the cytosine at CpG dinucleotides
CpG neucleotides enriched at the gene promotes (CpG islands)
catalysed by DNa methytransferases (DNMT)
what are CpG sites?
Along the linear DNA chain, there are sites of DNA where a cytosine is followed by and linked via a phosphate to guanine, another nucleotide
Regions of DNA that have a high density of CpG sites are called CpG islands.
DNA + Protein =
chromatin
DNa histones can be modified to affect?
chromatin structure
what is Acetylation
open the chromatin structure and activate transcription
- Histone acetyl transferase (HAT)
- Histone deacetylase (HDAC) reverses this
what three modifications can be reversed in epigenetics?
Acetylation
methylation
Phosphorylation
what is Phosphorylation
Condenses chromatin during cell cycle, but can also open it during remodelling
define methylation
augments the repression of transcription
what is x inactivation?
X-inactivation (also called lyonization) is a process by which one of the two copies of the Xchromosome present in female mammals isinactivated randomly (by chance) inactivated in an early embryonic cell, with fixed inactivation of that same X in all cells descended from that cell. The change that occurs with X inactivation is epigenetic: it is a heritable change in gene function without a change in the sequence of the DNA.
X inactivation is not restricted to females. It also occurs in males withKlinefelter syndrome who have more than one X chromosome.
what is x dosage compensation and what does it help?
Dosage compensation is the process that ensures equal levels of X-linked gene products in males and females in species in which the sexes differ in the number of X chromosomes they possess.
helps with x inactivation
name 4 diseases with an epigenetic component
cancer
schizophrenia
bipolar disorder
fragile x mental retardation
epigenetic changes are involved in
aging
regulation of genetranscription
x chromosone inactivation
autosomal chromosone imprinting
cellular differentiation
complex non mendalin diseases
sources of epigenetic marks?
nature: epigenetic marks can be inherited
nuture: epigentic marks can beaccumulated : only those in germ line will be passed down
define epigenome
complete epigenetic state of a cell
what is tRNA
Transfer ribonucleic acid (tRNA) is a type of RNA molecule that helps decode a messenger RNA (mRNA) sequence into a protein. tRNAsfunction at specific sites in the ribosome during translation, which is a process that synthesizes a protein from an mRNA molecule.
what is r RNA
ribosomal ribonucleic acid (rRNA) is the RNA component of the ribosome, and is essential for protein synthesis in all living organisms.
(rRNA) that which together with proteins forms the ribosomes, playing a structural role and also a role in ribosomalbinding of mRNA and tRNAs..
what is tRNA
Transfer ribonucleic acid (tRNA) is a type of RNA molecule that helps decode a messenger RNA (mRNA) sequence into a protein. tRNAsfunction at specific sites in the ribosome during translation, which is a process that synthesizes a protein from an mRNA molecule.
what is snRNA
small nuclear RNA (snRNA) a class of eukaryotic small RNA molecules found in the nucleus, usually as ribonucleoproteins, andapparently involved in processing heterogeneous nuclear RNA.
what is hnRNA
heterogeneous nuclear RNA (hnRNA) a diverse group of long primary transcripts formed in the eukaryotic nucleus, many of which willbe processed to mRNA molecules by splicing.
in RNA what is the template strand?
the 3’ to 5’ strand
prokaryotes vs eukaryotes
uCoupled Transcription and Translation (Pro)
uRNA Processing (Euk)
uPolycistronic (Pro)
uMonocistronic (Euk)
define genetics
the scientific study of heredity and the variation of inherited characteristics.
what does someone with a genetic disorder suffer from
–Substitution of one or more bases.
–Deletion or Insertion.
–Inversion.
–Translocation.
what is substitution
•Replacement of one base with another.
•Some have no effect due to redundancy of genetic code.•Eg DNA change from CCG to CCA, then mRNA changed from GGC to GGU.
But amino acid still glycine, no change
- May be an improvement = very rare, but evolution needs variation.
- But can cause severe disability eg sickle cell anaemia 1/1,600 black African people.
- Chromosome 11 affected.
what is sickle cell anemia
chromosone 11
Due to sickle haemoglobin in homozygotes
•Main effects due to:
–Obstruction of blood flow by less pliable sickle cells
–Anaemia caused by reduced lifespan of sickle cells (60 days instead of 120 days)
Heterozygotes have less severe symptoms
•Incomplete dominance
A balanced polymorphism.
examples of substitution
sickle cell anemia
PKU
•Phenylketonurea, chromosome 12. defective enzyme
•
•Haemophilia, X chromosome, lack of blood clotting factor.
•
•Duchene muscular dystrophy, X chromosome, abnormal muscle protein.
what are insertions/deletions in genetic disorders
•Additions or losses of one or more bases.
Can cause frame shift mutations
example of insertion/deletion genetic disorder
cystic fibrosis -
•Caused by deletion on chromosome 7 (in most cases)
what is inversion in genetic disorders
•a chromosome breaks and the piece of the chromosome turns upside down and reattaches itself•may or may not cause problems depending upon their exact structure
what is translocation in genetic disorders
- a rearrangement of a chromosome segment from one location to another, either within the same chromosome or to another.
- Eg. Robertsonian translocation leading to Down’s Syndrome – a rare cause.
label the structure of a gene
for natural selection to occur what three things must be met
•PHENOTYPIC VARIATION - variation among individuals in some attribute or trait.
•
•FITNESS VARIATION - a consistent relationship between that trait and the mating ability, fertilizing ability, fertility, fecundity, and/or survivorship.
•
•INHERITANCE - a consistent relationship for that trait between parents and their offspring which is at least partially independent of common environmental effects.
what three things must be met for random genetic drift
•PHENOTYPIC VARIATION - variation among individuals in some attribute or trait.
•
•RANDOM SAMPLING – one or other form of biological random sampling and subsequent sampling error.
•
•INHERITANCE - a consistent relationship for that trait between parents and their offspring which is at least partially independent of common environmental effects.
Relative importance of NS versus RGD
•Natural selection can only act when there are genotype dependent differences in the number of progeny.
•
•These differences may be measured by survivorship and fecundity.
define sucessful transformation (DNA manipulation)
Plasmid enters bacteria but does not recombine with DNA = episomal maintance of plasmid
in transformation (DNA manipulation) what three methods can be used to introduce holes into the bacterial cell wall
Electrical current, high temperatures, high salt concentrations can all be used to introduce holes in bacterial cell wall
what are the steps of DNA cloning
label this mitosis onion
label this mitosis sheet
label this mitosis sheet
in RNA splicing what does u1 do?
u1 snRNPs bind to intron
in RNA splicing what does u2 do?
binds to branch point
sequence (YNCURAY) upstream
of splice junction
in RNA splicing what does u4/u5/u6 do?
U4/U6 & U5 interact and combine
with U1 and U2 creating a loop
known as a LARIAT structure
in rna splicing what does u4 do
U4 dissociates creating an
ACTIVE SPLICEOSOME
what is a gene commonly defined as?
the entire
nucleic acid sequence that is necessary for the
synthesis of a functional gene product (protein
or functional RNA)
what are the properties of dna
Double helix – antiparallel strands
Minor and Major grooves
4 bases – purine and pyrimidines
A/C/G/T
Hydrogen bonds
Phosphodiester bonds
Glycosidic bonds
Alternate forms – A/B/Z
what is a chromatin
Complex of DNA, histones and non-histone proteins from
which eukaryotic chromosomes are formed.
what are neucleosomes?
NUCLEOSOME – Repeating unit; 8 histones surrounded by 145 nucleotide
pairs. Joined to next with linked DNA ~55bp
what are chromatosomes?
CHROMATOSOME – Nucleosome, linker and H1 histone
what is mitochrondial dna useful for
Evolutionary biologists to study the
variations between human and other
species in order to specify the
possible relationships between them.
– Molecular anthropologists and
genetic genealogists to examine
mtDNA of various populations to map
out ancestry and migration during the
years.
– Forensic scientists - HV1 and HV2
are hypervariable regions which are
often used for human identification in
cases of ancient DNA or highly
degraded DNA samples.
what is this?
neucleotide
adanine
dAMP - deoxyadonosine 5’ - monophosphate
what is this?
neucleotide
cytosine
deoxycytidine 5’monophosphate dCMP
what is this?
guanine
neucleotide
deoxyguanosine 5’ monophosphate dGMP
what is this?
thymine
neucleotide
deoxythymidine 5’ monophosphate dTMP
describe rna structure
Does not contain genetic material (some
exceptions in viruses)
Broader range of functions
Therefore replication not required
Intermediate between genes and protein
formation (mRNA)
Adaptor between codons (tRNA)
Ribosomal RNA (rRNA) associates with a set of
proteins to form ribosomes
Fold to form regions of double helix
Stem and loop formation
what is this
phosphodiester bond
describe dna replication
Mechanism of replication: separation of strands, specific coupling of free nucleic acids
First, the double stranded DNA must separate, or unwind. To do this:
DNA gyrase (class II topoisomerase) is responsible for uncoiling the DNA ahead of the replication fork. Helicase is responsible for unwinding the DNA at the replication fork. Single-strand binding protein (SSB) is responsible for keeping the DNA unwound after the helicase. SSBs stabilize single-stranded DNA by binding to it.
Next, you start making DNA that is complementary to the newly unwound/separated DNA. Note, all biological DNA synthesis occurs from the 5’ to the 3’ end.
Primase gets this started by laying down a short RNA primer on the unwound DNA. The primer is made of RNA, but is complementary to the DNA sequence. Later, this RNA is replaced with DNA.
DNA polymerase then takes over and makes DNA that is complementary to the unwound DNA.
DNA synthesis occurs on both strands of the unwound DNA. The synthesis that proceeds in the direction of the replication fork is the leading strand. The synthesis that proceeds in the opposite direction to the replication fork is the lagging strand. The lagging strand contains Okazaki fragments.
Finally, RNA primers are replaced with DNA by a special DNA polymerase. The Okazaki fragments in the lagging strands are then stitched together by DNA ligase.
DNA synthesis is bidirectional: 2 replication forks form and proceeds in opposite directions (like an expanding bubble).
Biological DNA synthesis always proceeds from the 5’ end to the 3’ end.
DNA polymerase has proof-reading activity, which means it corrects any mistakes (mutations) it makes.
Replication occurs once every cell generation, during the S phase. (Cell division may occur twice in meiosis, but replication still occurs once only)
define annealing
Annealing (biology), in genetics, means for complementary sequences of single-stranded DNA or RNA to pair by hydrogen bonds to form a double-stranded polynucleotide.
what is meant by ethics?
Dictionary definition – Moral Principles What is ‘right’ and ‘wrong’ Are we more ethical now than 50 years ago? Why? “Those who do not learn from history are doomed to repeat it” – George Santayana
what is an ethical issue?
A disagreement about what to do A conflict between moral principles
what is Beneficence
Serving the interests and wellbeing of others • Act in the best interest of the individual
what is Nonmalfeasance
do no harm, no official misconduct
what are the 5 freedoms
To make informed decisions • All persons treated equally • Confidentiality • Voluntary participation • Protect participants
what is consent
and what is informed consent?
consent
No coercion or inducement • No payment or reward (?) • No influence by researcher • No influence by family
informed consent
• What the research is for • Benefits/Risks • Presented in understandable manner • Time to consider and decide
Do you have any right to royalties from tests devised after researching donated tissues? Do these tissues still belong to you?
leagally no
morally - undecided
gel electrophoresis machine
label these
There are two different varieties of tomato plant, both are true breeding and both
have green stem colour. When these are crossed the F1 generation all have purple stems. However when the F1 are crossed to give the F2 the following ratio is produced; 9 purple stem : 7 green stem.
Consider how this result could be obtained.
This problem illustrates epistasis which is when the expression of one gene is influenced by another non-allelic gene. In order to develop the purple colour the plants must each have at least one of each dominant allele. It gives a modified dihybrid ratio.
what is epistasis
when the expression of one gene is influenced by another non-allelic gene.
Transcription factors include a wide number of proteins, excluding
RNA polymerase
