Genetics Flashcards
examples of proteins
-structural proteins
-enzymes
-hormones
Function of DNA
-Hereditary material responsible for passing genetic information from cell to cell
-carries instructions to make proteins(only one strand codes for manufacture of protein(template strand)
How is DNA adapted
-stable molecule
-2 strands can separate
-large molecule that carries lots of information
-base pairings prevents corruptions from outside chemical or physical forces
What are the four bases
Adenine
Thymine
Cytosine
Guanine
What are the base pairings
Cytosine - Guanine(3 hydrogen bonds)
Adenine - Thymine(2 hydrogen bonds)
What are the molecules found in a repeat unit of a nucleotide
Phosphate(circle)
Deoxyribose(pentagon)
Base(rectangle)
What is a gene
A section of a molecule of DNA which codes for a specific protein by specifying order in which amino acids must be joined together
What do proteins do
Give us our features
What are alleles
-Variations of the same gene
-gives rise to differences in inherited chracteristics
What is the genome
All the DNA found in an organism
What is RNA
-a polynucleotide, made up of many nucleotides linked together in a long chain
Differences between DNA and RNA
-DNA is double stranded, RNA is single stranded
-the sugar of DNA is deoxyribose, RNA is ribose
-DNA has thymine but RNA has uracil instead(still binds to cytosine
What are the two types of RNA
- Messenger RNA (mRNA)
- Transfer RNA (tRNA)
chromosomes
thread-like structures of DNA carrying genetic information in the form of genes, located in the nucleus of cells
How many pairs of chromosomes does an ordinary human body contain
23 pairs of chromosomes = 46 in total
What are chromosomes
-when the DNA double helix supercoils to form structures called chromosomes(in the nucleus)
What is a homologous pair
-a chromosome pair(not identical)
where are chromosomes inherited from
one chromosome from a pair is inherited from each parent
what is protein synthesis
the process of turning a gene into a specific sequence of amino acids that make up a specific protein
What is transcription
DNA is transcribed and an mRNA molecule is produced
Why is transcription needed
-DNA cannot leave nucleus as it is too big
-Ribosomes are found in the cytoplasm
-a copy of the gene must be made and transferred out of the nucleus
What is translation
-mRNA is translated and an amino acid sequence(protein) is produced
What is the sequence of events in the transcription of DNA
- transcription occurs in the nucleus
- RNA polymerase attaches to the DNA in a non-coding region just before the gene
- two strands of DNA unzip by breaking weak hydrogen bonds. Done by the RNA polymerase enzyme
- RNA polymerase moves along DNA strand
- Free nucleotides form hydrogen bonds with exposed DNA strand by complementary base pairing
- mRNA is the opposite copy of DNA strand, mRNA is a complementary copy
- Newly formed strand is ready to leave the nucleus and travel to ribosomes which are located in the cytoplasm
where does transcription occur
in the nucleus of the cell
where does translation occur
occurs in the cytoplasm of the cell
process of translation steps
-mRNA arrives at ribosome
-mRNA has codons
-ribosome move long mRNA strand
-tRNA brings amino acid to ribosome
-anticodon binds with codon
-amino acid chain produced/polypeptide
phenotype
observable characteristics of an organism
Genotype
combinations of alleles that control each characteristic
dominant allele
an allele that is always expressed
recessive allele
allele that is expressed only when there is no dominant allele
homozygous
if the two alleles of a gene are the same, the individual id described as homozygous
heterozygous
if the two alleles of a gene are different, the individual id described as being heterozygous
gamete
sex cells
codominant
both alleles within a genotype are expressed in the phenotype of an individual
genotypes of blood
Iᵃ Iᵃ or Iᵃ Iᵒ = A
Iᵇ Iᵇ or Iᵇ Iᵒ = B
Iᵃ Iᵇ = AB
Iᵒ Iᵒ = O
polygenic
characteristics that are controlled by more than one gene
example of polygenic inheritance
eye colour
shape of male and female in family pedigrees
Male = Square
Female = Circle
colour of affected and unaffected individuals in family pedigrees
Red = affected
Blue = unaffected
male and female chromosomes
Male = XY
female = XX
Mitoses
type of cell division that produces diploid body cells identical to parent cell
use of mitosis
-growth
-repair of damaged tissues
-asexual reproduction
(-replacement of cells)
order of meiosis and mitoses in terms of phases
interphase
prophase
metaphase
anaphase
telophase
interphase
-DNA in chromosomes replicate itself, ready for mitoses
-cell spends most of its life here
prophase
-chromatids condense and become visible
-the nucleus membrane disappears
metaphase
-structure called the spindle forms
-chromatids line up at the equator
-spindle attaches to them by their centromeres
Anaphase
-Spindle fibres shorten and pull the chromatids into the poles of the cell
-Chromatids separate
telophase
new membrane form around the chromosomes at each end of cell
-two new nuclei therefore forms
-cytoplasm starts to divide to produce two daughter cells
-both daughter cells have a copy of each chromosomes from the parent cell
cytokinesis
the division of the cytoplasm at the end of meiosis or mitosis, bringing about the separation into two daughter cells
meiosis
type of cell division that produces haploid gametes, genetically different to each other and parent cell
differences between mitosis and meiosis
-mitoses produces cells with diploid number of chromosomes, meiosis haploid
-two daughter cells produced in mitosis, 4 in meiosis
-daughter cells are genetically identical to each other and parent cell in mitosis, daughter cells are genetically different from each other and parent cell in meiosis
-one cell division in mitosis, 2 in meiosis
fertilisation
fusion of male and female gametes to form a zygote
zygote
single cell resulting from fusion of male and female gametes
differentiation
the process by which cells become more specialised and different from each other as they mature
what causes differentiation
involves the expression of some genes and not others
stem cell
immature cell that has the potential to differentiate into a specialised cell type
what can stem cells do
-differentiate into specialised cells
-divide repeatedly
-form more stem cells
where are embryonic stem cells obtained from
extracted from very early embryos and are grown in laboratory incubators
how to scientists make embryonic stem cells differentiate into the cell type that is required
add growth factor chemicals
what type of cells can embryonic stem cells turn into
any type
how are adult stem cells obtained
-extracted from body tissues and grown in laboratory cultures
what type of cells can adult stem cells differentiate into
-a limited number of different cell types
advantages of embryonic stem cells
-can make any cell type
-puts spare embryos from IVF to good use and can improve other people’s lives
disadvantages of embryonic stem cells
-their use could be considered as killing a potential human life
-difficult to grow in a culture, production is inefficient
-difficult to make them differentiate into the right type of specialised cell, can result in cancer
-comes from donor so immune rejection can occur
adult stem cell advantages
-no potential human lives destroyed
-if a patient’s own cells are used the body will not reject them
-differentiation process is easier to control as it has already started, less likely to cause tumours and cancers
disadvantages of adult stem cells
-can be difficult and painful to extract
-cannot differentiate into all cell types
stem cell therapy
use of stem cells to repair damaged tissues
mutation
-rare, random change in genes or chromosomes
how many codons are there for each amino acid
generally more than one
what do mutations do
can cause a change in the base sequence
what are the possible outcomes of a mutation
-neutral: the new codon can code for the same amino acid, protein stays the same and no change in the phenotype is seen
-harmful: the correct protein is no longer coded for
-advantage: can result in a benefit to the organism (antibiotic resistance DNA)
Causes of Down syndrome
-failure of chromosome to separate
-gamete has extra chromosome
-normal egg fertilised by abnormal sperm
Causes of Down syndrome
-failure of chromosome to separate
-gamete has extra chromosome
-normal egg fertilised by abnormal sperm
