Genetics Flashcards
Describe double helix
A spiral molecule made of 2 strands of DNA joined by bases. Contains the genetic information in a linear sequence of chemical subunits called nucleotides
What are 4 bases in DNA?
Adenine
Thymine
Guanine
Cytosine
What is DNA?
Deoxyribonucleic acid. 2 strands of nucleic acids on sugar phosphate backbone formed in double helix.
What is a chromosome?
Strand of DNA and protein. The DNA and histones make up nucleosomes. The nucleic acid and histones are known and chromatin. The chromosome is almost 5cm long so it twists and twists and twist to form recognisable X shape.
What is a gene?
Section of DNA containing particular set of instructions related to bodily function
How do bases join together?
A-T for example join together by hydrogen/polar bonding (a weak bond)
How do bases join to the deoxyribose strands?
covalent bonds
What are 4 bases in RNA?
Adenine
Cytosine
Guanine
Uracil (instead of thymine)
Describe how DNA becomes protein
DNA - transcription - mRNA - travels out of nucleus and attaches to ribosome - translation in groups of 3. t RNA bring along the amino acid which forms string to make protein.
What are codon and anti-codon?
codon = mRNA anti-codon = tRNA
How many chromosomes in each cell?
23 pairs = 46 in total
What are stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
Describe mitosis cycle
Prophase - DNA organises and condenses into chromosome shape. Nucleolus disappears. Centrosomes start to form microtubules
Pro Metaphase - nuclear membrane breaks down. Microtubules attach to kinetocre
Metaphase - chromatids align along the middle
Anaphase - Microtubules shorten, pulling chromatids apart
Telophase - Now have 46 chromatids at each pole. Microtubules break down. Nuclear membrane forms at each end. Chromosomes uncoil into uncondensed state
Cytokinesis - division of cell
Describe interphase
G1 - growth phase
Cell performs functions and duplicates organelles
S - synthesis - duplicates DNA
G2 - grow to final size
What does meiosis produce?
Gametes - haploid cells. (23 single chromosomes)
What is process where genetic information is changed?
Crossing over during prophase I or called recombination
What makes up chromosomes?
DNA and histones (protein). 2 chromatids with centromere in the middle = chromosome
What are autosomes?
All pairs of chromosomes that are not sex chromosomes
What is an allele?
The small section of chromosome that codes specific gene
What is autosomal dominant inheritance?
Abnormal gene on one of the non-sex chromosomes.
Males and Females express the allele and transmitted equally to sons and daughters.
Ratio of affected to unaffected children = almost always 1:1
50% chance of each child being effected
Every affected person has an affected parent
What are x-linked disorders?
Abnormal gene on X
Who is usually affected by X linked disorders?
Males
Give 4 examples of X-linked disorder
Duchennes MD
Haemophlia
Colour blindness
Fragile X
Give 4 examples of autosomal recessive disorder
CF
Sickle Cell
Thalasemia
Tay-Sachs
Give 2 examples of autosomal dominant disorder
Neurofibromatosis
Tuberus sclerosis
What is difference between phenotype and genotype?
Genotype = genetic code Phenotype = physical characteristics
Describe RNA
Determines the amino acid composition of proteins, which in turns determines the function of the protein and therefore the function of that particular cell
Describe an amino acid
A simple organic compound containing a carboxyl and an amino group
What is difference between dominant and recessive gene?
Dominant gene exerts its effect when present on only one chromosome
Recessive gene has to be present on both chromosomes in order to manifest itself.
What is autosomal Recessive inheritance?
2 copies of abnormal gene must be present
Children usuallyy affected but not the parents
1:4 chance of each pregnancy being affected
Some carriers can express variations in genetic disease expression
What are x-linked disorders?
Mother a carrier
Usually unaffected
Female carriers - X chromosomal dominance cancels out the affected other X chromosomes
Name 4 syndromes are chromosome related?
Trisomy 21
Turners Syndrome
Edwards Syndrome
Kleinfelters Snydrome
What happens in prophase of mitosis?
Nucleolus disappears
DNA starts to condense and form characteristic X shaped chromosomes
Centrosomes start making tubules
What happens in pro metaphase of mitosis?
Nuclear membrane breaks down
Microtubules grow and attach to kineticore on each chromatid.
What happens in metaphase of mitosis?
Chromosomes align along middle of cell
What happens in anaphase of mitosis?
Microtubule fibres start to shorten - pulling chromatids apart to either end of the cell.
What happens in telophase of mitosis?
Microtubules break down
Nuclear membrane forms around each set of chromosomes (23 pairs)
Chromosomes uncondense and go into uncoiled state.
Then cytokinesis where the cell divides.
What happens in interphase of mitosis cell cycle?
G1 - growth stage. Cell grows and performs functions. Duplicates organelles
S - synthesis. DNA is duplicated.
G2 - growth stage to final size
What happens in prophase I of meiosis?
DNA condenses
2 pairs of sister chromatids align and have recombination of genetic material ‘crossing over’
Centrosomes head to poles and start making microtubules
nuclear membrane breaks down
What happens in metaphase I of meiosis?
Chromosomes align along equator in random order (hence different combinations of genetic material in gametes)
What happens in anaphase I of meiosis?
Microtubules shorten and pull chromatids apart. Sister chromatids remain attached.
What happens in telophase I of meiosis?
Cell separates into 2 cells.
