Genetics Flashcards
What is classification?
Placing objects into similar groups or categories
How are things classified?
Similarities in structure, function and development
What is the basic unit of classification?
Species
What is a species?
Group of similar organisms that are capable of naturally interbreeding with eachother to produce fertile offspring
What is variation within a species?
In a group of successfully interbreeding organisms, the individual members show different characteristics
How can members within a species differ in humans and plants
Human - hair colour, skin colour, height
Plant - flower colour, leaf shape
What is acquired variation and give an example
Not inherited/not genetically controlled and therefore learned and developed
Eg, ability to speak language, learn piano
What is inherited variation and give an example
Controlled by genes eg, ear shape
What is heredity?
It’s the passing on of features from parents to offspring by means of genes
What are the units of heredity?
Genes
What are characteristics?
Traits/features that are inherited genetically
What are genes?
Section of DNA that can cause production of protein
The proteins produced by genes are mainly what?
Enzymes
Why/how do genes control a cell
Enzymes they produce control cell activities
Where in the nucleus would you find genes?
On a Chromosome
What is gene expression?
It’s the precise way in which the genetic information in a gene is decoded in the cell and used to make protein
What are chromosomes composed of?
Protein and DNA
What protein is present in chromosomes?
Histone
What is the role of protein in chromosomes?
It’s responsible for holding DNA in a tightly packed configuration so it can fit nucleus
What is the function of non-coding dna
It is not known - it’s known as “junk DNA”
Name the key chemical that is inherited by organisms
Genes
What is coding and non coding DNA
Coding - DNA capable of gene expression to produce protein
Non-coding DNA - not capable of gene expression to produce protein
Where in the cell would you expect to find most DNA?
Nucleus
Name the four bases that are found in DNA
Cytosine, Guanine, Adenine, Thymine
What is meant by a triplet code?
Sequence of three bases which codes for one specific protein
The triplet code is transcribed into mRNA. What does this statement mean?
Info [code] is copied from DNA to RNA
To which structures in the cell does mRNA carry the code?
Ribosome
Which base can link only to thymine?
Adenine
Which base can link only to cytosine?
Guanine
Name the type of bonding which occurs between members of a base pair
Hydrogen bonding
Explain what is meant by the term DNA profiling
Examining DNA for a pattern/band to compare
Method of making a unique pattern of bands from the DNA of a person, which can then be used to distinguish that DNA from other DNA
Give two applications of DNA profiling
Forensic [identify criminal]
Maternity/paternity determination
What is genetic screening?
Testing DNA for the presence or absence of altered/abnormal genes
The same amount of DNA is present in the nuclei of cells taken from the liver, heart, pancreas and muscle of a rat.
Use your knowledge of DNA and mitosis to explain this statement
Chromosome contains DNA
Mitosis maintains same chromosome number
The same amount of DNA is present in the nuclei of cells taken from the liver, heart, pancreas and muscle of a rat.
Name a dell produced by the rat which will contain a different amount of DNA in its nucleus to those mentioned above
Gamete
Give a brief account of the stages involved in DNA profiling
DNA released
DNA cut into fragments by restriction enzymes
Fragments separated on basis of size of gel
Pattern analysed
Labelled diagram of a nucleotide
Check notes
Phosphate, deoxyribose, base
What part of a nucleotide may vary from nucleotide to nucleotide
Base
What is meant by non-coding DNA
Does not code for protein
Give one structural difference between DNA and RNA
DNA - thymine
RNA - uracil
Name a cell organelle apart from the nucleus in which DNA is found
Mitochondria
Chloroplast
Describe fully the roles played in protein synthesis by the three different types of RNA
mRNA - gets code from DNA and carries code to ribosome
rRNA - binds mRNA in place for translation
tRNA - transfers amino acids to mRNA to ribosomes
Once a protein has been sythesised, a final step is required for it to become fully functional. What is this step?
Folding
Write notes on the following topics in relation to nucleic acids
i) Complementary Base Pairs
ii) Codons
iii) Transcription
i) Two bases joined by hydrogen bonds, Adenine bonds to Thymine and Cytosine bonds to Guanine in DNA, in RNA thymine is replaced with Uracil
ii) sequence of three bases which codes for one specific amino acid/protein in DNA
iii) mRNA is formed using single strand of DNA, catalysed by RNA polymerase
Name the biomolecule that is the major component of meat
Protein
Where in the cell are protein manufactured?
Ribosomes
Name the molecule formed from DNA, which carries the instruction to manufacture proteins
mRNA
Name the procedure used for analysing the DNA samples that revealed the presence of horse meat in products labelled as beef
DNA Profiling
Would the result from DNA Profiling be the same if beef were contaminated with pig meat
No, because pig DNA is not same as Horse DNA
What are the subunits of nucleic acid found in DNA?
Nucleotides
How are the strands of a DNA molecule joined together?
Hydrogen Bonds
What are the two main events in the replication of DNA
DNA opens and new strands of DNA are made
Explain the term transcription
Making mRNA using DNA (template)
Explain the term translation
Making protein using code from mRNA [RNA template]
In which structures in the cell does translation occur?
Ribosomes
How many bases in sequence make up a codon in mRNA
Three
Each mRNA codon specifies one of three possible outcomes during protein synthesis. Name these three possible outcomes
Start, adding an amino acid, stop
What does the letter ‘t’ stand for in tRNA?
Transfer
During translation, what are attached usually to the two ends of the tRNA molecules
mRNA codon and an amino acid
What percentage of chromosomes are DNA?
40%
How do two strands of DNA match up?
Specific base pairing between just four bases
What are the
i) two purines
ii) two pyramidines
i) adenine, guanine
ii) thymine, cytosine
Strands of DNA are anti-parallel, what does this mean?
Strands of DNA run parallel to each other but in opposite directions
What is another word for non-coding DNA?
Introns
What percentage of DNA is non-coding?
97%
What is another word for coding DNA?
Exons
What are the differences between RNA and DNA
DNA - Sugar -> Deoxyribose Thymine instead Double stranded RNA - Sugar -> Ribose Base uracil instead Single stranded
Give two examples of genetic disorders
Cystic fibrosis
Albanism
How is genetic screening used for adults?
Although they do not suffer from a genetic disorder they may carry a defective gene that may want to find out if they are a carrier of that gene or not
What are the ethical reasons behind genetic screening?
Is it better to be prepared for disorder?
Would person wish to know if they have a genetic disorder that will develop on later years?
When does DNA replication occur?
Interphase of cycle
Describe the events that occur in the replication of DNA
[look at page]
The double helix uncoils [rope-ladder]
Enzyme breaks the bonds between the base pairs
DNA bases that are naturally present in cytoplasm enter the nucleus. The incoming bases attach to the exposed complementary bases. In this way, each side of the DNA molecule acts as a template for the new DNA that is formed
Each new strand is half new and half old and identical to the original DNA strand and to the other new partner strand
Each new piece of DNA rewinds to form a double helix
What occurs during transcription in protein synthesis
DNA is uncoiled and separated by enzymes in nucleus
Complementary RNA bases [A,U,G,C] bond with one of the exposed DNA strands
RNA polymerase joins with RNA bases together to form mRNA
Each mRNA carries a start codon, a series of codons to form specific amino acids, a stop codon
What occurs during translation in protein synthesis
mRNA moves from the nucleus to the cytoplasm
Ribosomes are made of rRNA and protein
The mRNA bonds weakly with the rRNA in the ribosome
tRNA carries a special triplet [anti-codon] and an amino acid [AA6, AA12]
tRNA attaches to the mRNA [each anticodon pairs up with the complementary codon on the mRNA, bringing an amino acid to ribosomes]
The tRNA lines up along the mRNA strand and each adjacent amino acid join up to form a protein chain. The amino acids detach from the tRNA
tRNA leaves the ribosome without aa’s pulling the mRNA with it allowing the mRNA sequence to be completed and a new protein being formed until the stop codon is reached
A protein is made when the stop codon is reached [synthesised]. This protein undergoes further folding to reach the correct shape of that protein
What is the site of protein synthesis
Ribosome
Where is mRNA found?
Nucleus, cytoplasm and ribosome
Where is tRNA found?
Cytoplasm
Where is rRNA found?
Ribosome [where proteins are made]
Describe the method you took when you isolated DNA from plant tissue
Sodium chloride was added to washing up liquid and distilled water was added to 100cm^3
Cut onion into small cubes and add to beaker and stir
Put beaker in water bath for 15 mins @ 60
Cool mixture in ice water bath 5 mins, stirring frequently
Pour mixture in blender and blend for 3 seconds
Filter mixture with coffee filter paper in second beaker [don’t add foam]
Syringe [no needle] used to place onion filtrate into boiling tube
Add protease enzyme [pepsin] to boiling tube and mix well
Pour ice-cold ethanol down side of boiling tube and the ethanol will form a layer on onion filtrate
Twist glass rod with wire loop in alcohol and the strands of DNA should attach to rod.
-isolate DNA-
Why must you chop the onion to small pieces
Physical chopping breaks the cell walls and allows the cytoplasm to leak out
-isolate DNA-
Why is washing up liquid added?
Breaks down lipids in phospholipid bilayer and causes protein in the membranes to break apart. This results in the release of the nuclear material from the cell
-isolate DNA-
Why is salt added?
To minimise the attractive forces present between DNA and protein by shielding the DNA molecules causing them to clump together
-isolate DNA-
Why is the mixture heated to 60 degrees for exactly 15 minutes
Causes DNases, released from lysosomes to be broken down
-isolate DNA-
What happens if the mixture is heated for more than 15 minutes
DNA itself will be broken down
-isolate DNA-
Why is the mixture cooled?
Decreases the rate of chemical reactions, slowing the action of any remaining enzymes before they destroy the DNA
-isolate DNA-
What is the function of blending?
Further destroys cell walls and membranes, causes DNA to be released
-isolate DNA-
What occurs if the mixture is blended for more than three seconds?
It shears the fragile DNA strands
-isolate DNA-
Why is protease added?
Breaks down proteins associated with DNA
-isolate DNA-
What is the mixture filtered with?
Coffee filter paper
-isolate DNA-
What is the purpose of filtering?
Strains all the large cellular debris out of the mixture. DNA is passed through the filter with the liquid
-isolate DNA-
Why is cold ethanol used?
Forms a layer on top of the onion filtrate and tends to draw water out of DNA molecule making it less dense. DNA is insoluble in cold ethanol
-isolate DNA-
Where are the DNA strands found in the mixture?
Interface of the two liquids
The son of a haemophiliac father was not haemophiliac. Explain in detail how this situation might have arisen
The haemophilia gene is recessive and sex linked
The father has to be XYn- and the son doesn’t have haemophilia meaning he has to be XYN-
The mother can be XXNN or XXNn
Son would get XN from egg and Y- from sperm meaning he does not haemophilia
In genetics what is meant by sex-linkage
Genes are carried on the sex chromosomes
Would human females or males be more likely to suffer from sex linked diseases such as haemophilia. Explain your answer by referring to possible genotypes and corresponding phenotypes
Males Males - XYn- sufferer Females - XXnn sufferer XXNn normal Males only needs to inherit recessive allele and female needs both recessive alleles from each parent
In certain breed of cattle there is incomplete dominance between alleles for red coat and allele for white coat. The heterozygous individuals are roan. In each of the following write the percentage chance it will have a red coat
i Roan x White
ii)Roan x Red
iii)Roan x Roan
i) Rr x rr = O%
ii) Rr x RR = 50%
iii) Rr x Rr = 25%
Which famous 19th Century biologist is regarded as “the father of genetics”
Mendel
In genetics what is meant by segregation
Separation of homologous chromosomes
Give two examples of sex-linked characteristic in humans
Haemophilia, colour-blindness
Two heterozygous chromosomes, one male and one female. Which will produce the greatest number of different gametes
Female
Sex
Combinations
Write out genotypes of gametes that the bird with gl linked and gl linked who is a man
Xgl Ygl
What term is used to describe the allele pair Pp and is this a sex-linked condition?
Heterozygous
No, genes are not carried on x or Y chromosomes
[cattlee breed where P = hornless is dominant to horned]
Draw a chromosome diagram when crossed with Pp XY would ensure the production of a hornless calf
PP XX
Name a group of organisms in which XY chromosome pair gives rise to a different sex in cattle
Birds, Butterflies, Moths
Human males and females differ in one of their twenty three pairs of chromosomes. What name is given to this pair of chromosomes
Sex chromosomes / Heterosomes
Draw the two sex chromosomes for human male and human female
Male - XY I short I
Female - XX II
Using a punnet square, that a child stands an equal chance of being male or female
X Y
X xx xy
X xx xy
XX, XX, XY, XY
50% 50%
[The allele for smooth is dominant to wrinkled and the allele for yellow is dominant to green]
Give genotype of pea plant that’s homozygous in respect to seed texture and heterozygous in respect of seed colour
SSYy
Smooth and yellow
Give another genotype which will produce the same phenotype as SsYy
SSYY
The allele for smooth is dominant to wrinkled and the allele for yellow is dominant to green
Allele for smooth is linked to allele for green and the allele for wrinkled were linked together yellow give the genotypes of two gametes that parent SSYy can produce
Sy
sY
What is the significance of the fact that the two allele pairs are located on different chromosome pairs
Independent assortment can occur
What is an allele?
Different form of same gene
What is homozygous
Two identical alleles
What is heterozygous
Two alleles are different of a gene
What is linkage?
Genes on same chromosome
What is a locus?
Position of a gene on a chromosome
What is a dominant allele
Allele that prevents the working of the recessive allele/who masks the expression of recessive
What is a recessive allele
Allele is prevented from working by a dominant allele/whose expression is masked by dominant
What is a genotype
Genetic make up of an organism
What is a phenotype
Physical make up of an organism which is the expression of the genotype
What is the progeny
Offspring produced
What is haploid and diploid
Haploid - nucleus with 1 set of chromosomes
Diploid - nucleus with two sets of chromosomes
What term is used to describe alleles that lie on the same chromosome?
Linked
How many loci are marked in the diagram
Linked AB and ab, non-linked Dd and Cc
4 (each pair of allele is one locus)
How do you know whether or not alleles are linked?
on same chromosome or not
Suggest why a person with a heterozygous allele pair does not suffer from the condition
Dominant allele masks expression of recessive allele
Parents who are suspected of being carriers of disease-causing alleles may be advised to consider a genetic test. Suggest a role for such test after in-vitro fertilisation
Selection of embyro
Explain why linked genes do not assort independently
They are transmitted together on same chromosome
What term is used to describe a person who has a gene for colour blindness but who does not exhibit the condition
Carrier
If a colour blind father and a mother who is heterozygous for this condition, is it possible to have a colour blind daughter and briefly explain your answer
Yes, both parents carry gene for colour blindness
Where is mRNA found
The nucleus and cytoplasm in a cell
Is down syndrome a condition caused by a gene mutation
No, it occurs due to a change in chromosome number
Where does transciption occur in a cell
Nucleus of cell
Explain the significance of DNA replication
Exact copies of DNA is passed from generation to generation
Name an enzyme involved in transcription
RNA polymerase
What do tRNA molecules carry to aid this process
Anticodon
Why is it necessary for folding to occur once the protein has been formed
Correct shape needed to carry out function
Are somatic cells diploid or haploid
Diploid - contain two of each type of chromosome
What produces the phenotype?
Interaction of genes with environment
Genotype + environment = phenotype
What are monohybrid crosses
Involves the study of a single characteristic
What are autosomes and how many do we have?
Non-sex chromosomes
44
How many chromosomes do we have and how many are sex chromosomes?
46 chromosomes
Two sex chromosomes
How is the sex of a child determined
Genotype of the sperm that fertilises the egg
[fathers sperm that determines the sex of the child]
What are dihybrid crosses?
Study of two characteristics at the same time
Why is haemophilia more common in males than in females
Males need only single recessive allele to be haemophiliac whereas females need two recessive alleles
What is Mendel’s second law? [Law id Independent Assortment]
It states that when gametes are formed either pair of the alleles is equally likely to combine with either of another pair of factors
What is Mendels first law? [Law of Segregation]
Inherited characteristics are controlled by pairs of factors, these factors segregate from each other at gamete formation, with only one member of the pair being found in each gamete
What is genetic engineering?
Artificial manipulation or alteration of genes
Give an example of genetic engineering in a
i) plant
ii) animal
iii) micro organisms
i) gene for vitamin A from daffodil is inserted into rice
ii) gene for human growth hormone from human inserted into cows milk
iii) gene for human insulin is inserted into bacterium e.coli
What are the four tools for genetic engineering
Source of DNA [cell containing target gene]
A cloning vector [bacterial plasmid]
Restriction enzymes [cut bases at specific base sequences]
DNA ligase [pasting DNA]
What are the five processes in genetic engineering?
Isolation Cutting Ligation Transformation Expression
What occurs in isolation in genetic engineering
Target gene on its chromosomes must be released from the donor cell
Plasmid must be released from bacterial cell
What occurs in cutting in genetic engineering
Plasmid DNA cut by restriction enzymes at specific base sequences
The chromosome with target gene gets cut many times by same restriction enzyme at same base sequence
What occurs in ligation in genetic engineering
Enzyme DNA ligase used to join up target gene DNA with plasmid DNA. The ends match due to the fact both DNA’s are cut by same enzymes
What occurs in transformation of genetic engineering
The host DNA is now different - or “transformed”
What occurs in expression of genetic engineering
Gene is expressed once protein is produced on target gene
Give two ethical/moral issues surrounding genetic engineering
Release of GMO’s into environment -> it genetically modified plants are grown outdoors, there are fears that foreign genes they contain might spread to other plants
Genetic engineering in humans -> inserting/removing gene from sperm or eggs and zygotes is at present not acceptable, form of eugenics
In the context of natural selection, explain how numbers in a population remain relatively constant despite the production of many offspring
Competition
Best adapted to survive
Death rate equals reproductive rate
Outline the role of natural selection in evolution
Better adapted to survive and this adaption is inherited
Explain the term mutation
Change in amount of structure of DNA
Give one example of a disorder caused by gene mutation
Sickle cell anaemia
Give one example of a disorder caused by chromosome mutation
Down syndrome
Give one cause of the differences which exist between individuals of a species
Sexual reproduction
Meiosis
Independent Assortment
Mutations
Give a source of evidence for evolution and briefly outline the evidence
Fossils - change over time which allows to be compared
Study of embryos [embryology] -the greater the similarity in structure, the more closely related the species are and the more recent their common ancestor is.
Name two types of mutation
Gene mutation
Chromosome mutation
Name two agents responsible for increased rates of mutation
[mutagens]
UV light
X-rays
Briefly explain the significance of mutation in relation to natural selection
New phenotypes = better adapted
Name the scientists responsible for the theory of natural selection
Darwin and Wallace
What is meant by variation?
Differences between individuals of the same species
What is the significance of inherited variation in the evolution of species
Inherited variation which produces new genotypes allows natural selection to occur and thus evolution
Give an account of the Theory of Natural Selection. Name the scientists who are associated with the theory and refer to any one observation that promotes its development
A species produces a large number of offspring and has a high reproductive rate
Then, the population of the organisms remain constant due to competition or the struggle for survival and the environment no longer able to support them
Some organisms show genetic variation because of sexual reproduction [breeding] which are passed on
Darwin and Wallace
Observation - population no’s remain constant
-isolate DNA-
What is a protease enzyme?
Breaks down protein
-isolate DNA-
The final separation of the DNA involves the use of alcohol [ethanol]. Under what conditions is the alcohol used
Ice cold
How does meiosis cause inherited variation
Human cells have 46 chromosomes with millions of combinations of chromosomes
How are mutations inherited?
Mutations may be inherited by zygote and passed onto all the cells in the child
What are mutagens
Agents that cause mutations
Give an example of a mutation caused by mutagens
Tobacco smoke - causes mutations in a gene called P53
How does one protect against mutations
X-rays - wear heavy lead shield to absorb xray
UV rays - wear high sun protection factor
What is sickle cell anaemia
Example of gene mutation
Inherited blood disorder caused by a mutation in the haemoglobin gene
What is evolution?
The way in which living things change genetically to produce new forms of life over long periods of time
What is the conclusion drawn from overbreeding
Struggle for existence [competition]
What is the conclusion drawn from population no’s remaining constant
Natural selection
What is the conclusion drawn from inherited variations occur in population
Natural selection
What is natural selection
Process by which organisms with genetically controlled characteristics that allow them to be well adapted to their environment will survive and reproduce to pass on their genes to following generations
Give an example of evolution
Evolution of horse
60 million years ago - ancestor was size of fox
30 million years ago - size of german Shepard
15 million years ago - size of Great Dane
