Genetic variation Flashcards
Form of variation without mutation?
Crossing over
Term for chromosomes after crossing over?
Recombinant
Mutations?
Heritable changes in genetic material not due to genetic recombination
Can mutations in gametes be passed on?
Very small chance but not 0
Point mutations?
Changes in single base/small piece of genetic material
Purines?
A & G
Pyrimidines?
C and T
Transitions?
A to G or C to T
Transversion?
purine to pyrimidine
Transversions or transitions most common?
Transitions
Which quality of the genetic code means some changes don’t alter the amino acid?
It is redundant
Highly redundant amino acid?
Arginine
Amino acid only coded for by ATG?
Methyline
Non-synonymous change?
Amino acid changed
Synonymous change?
Amino acid doesn’t change
Most likely change?
Synonymous
Least likely change?
Removal of a start/addition of a stop codon
Mutation with serious consequences for protein?
Removal of a start/addition of a stop codon
Do mutations happen more often at synonymous site?
No - they’re just more likely to be tolerated & maintained in population at a synonymous site
Do all non-synonymous changes have serious consequences for the protein?
Some are minor & can be tolerated
Phenotype for sickle cell anaemia? (4)
- abnormal beta chains
- haemoglobin stick together & form chains
- sickle shaped deoxygenated red blood cells
- reduced life expectancy
Genotype for sickle cell anaemia? (3)
- amino acid 6
- base position 2
- GGA to GTA (Glu to Val)
What type of DNA do INDELs typically occur at?
Repetitive sections of DNA
Are INDELs common in genomes?
Yes
Why are INDELs common in genomes?
Only small proportion of genomes genes - repetitive DNA tends not to be in genes
Minisatellites?
10 to 15 base pairs in length
Microsatellites?
1 to 5 base pairs in length
Genetic fingerprinting? (3)
- sections of DNA that vary in size
- apply current
- small sections migrate further in agarose gel than larger
What can genetic fingerprinting be used for?
paternity tests, forensics, conservation genetics
Cystic fibrosis phenotype? (3)
- incorrectly folded protein
- thick, sticky mucus in lungs
- shortened life expectancy
Cystic fibrosis genotype? (4)
- result of different mutations
- most common deletion of 3 nucleotides in CTFR gene
- loss of amino acid phenylalanine
- doesn’t impact rest of chain
CTFR gene?
cystic fibrosis transmembrane conductance regulator
Inversions?
sections of DNA broken off & reinserted incorrectly
Result of inversions?
genes in chromosomes in wrong order
Inversions can be induced by…?
radiation
What can inversions in heterozygotes prevent?
crossing over
How can inversions prevent crossing over?
maternal & paternal alleles can’t align
Result of inversions preventing crossing over? (2)
- no recombination, genetic information lost
- due to accumulation of genetic changes over time, two populations prevented from breeding with each other
Problem with gene duplications?
not all genes can tolerate extra copies
How many transposable elements can be found in a typical genome?
Dozens to hundreds
How much of eukaryotic genome are transposable elements?
up to 90%
How much of human genome are human elements?
> 50%
Two ways in which transposable elements can move?
copy - and - paste
cut - and - paste
Transposable elements?
Copied section of DNA
What does ‘mobile’ mean in terms of transposable elements?
Can move around genome between generations
‘activator’ concerned with transposable elements?
can transpose and can move
‘dissociator’ concerned with transposable elements?
can’t transpose or move
Which other aspect can the activator move?
the dissociator
What does the activator moving the dissociator result in?
interrupted molecular pathway of gene, potentially non-functional
Can sections of DNA move more than once during development?
Yes
Purple kernels?
No transposition - normal gene expressed
Colourless kernels?
‘activator’ causes ‘dissociator’ to transpose onto gene
Spotted kernels?
‘activator’ causes ‘dissociator’ to transpose out of gene in a few cells during development
mutations in some cells reverts to normal gene
Do retrotransposons move via copy-and-paste or cut-and-paste?
copy-and-paste
Transposable elements size?
5 to 10 kilabases
What can two transposable elements near each other cause when aligning through crossing over?
duplication, deletion, inversion if facing each other
Do all individuals of a species have the same number of transposable elements?
no
Unequal crossing over?
crossing over at the wrong location
What can unequal crossing over result from?
transposable elements or due to any region of homology causing mistake in pairing
Diploid?
2n
Tetraploid?
4n
Hexaploid?
6n
Octaploid?
8n
Do species have to be diploid to be considered ‘normal’?
no
Which cells should be haploid?
gametes
What causes production of diploid gametes?
mutation: self-fertilization occurs
One way in which tetraploid organisms can be formed?
parents with unreduced gametes
What can the first generation tetraploid offspring do? (3)
- self-fertilize
- mate with 4n sibling
- back cross to parents
Backcrossing?
mating of offspring with parents or organism genetically similar to parents
Protist Oxytricha trifallax? (3)
- 15,600 nanochromosomes
- 2,000 copies of each chromosome
- 96% non-coding DNA
How many chromosomes does an ant have?
2
Why does a butterfly have so many chromosomes?
fallen apart, still maintained in genome as no loss of fitness
What increases genetic variation?
mutations occurring randomly