Mutation and variation Flashcards
Define a mutation.
Any heritable change to genomic DNA.
Are changes to whole chromosomes possible, or simply to single bases?
Both are possible.
Recessive mutations typically cause what?
A loss of function.
Dominant mutations typically cause what?
A gain of function.
What do conditional mutations depend on in order to be expressed?
The correct environment.
What will lethal mutations do?
Kill the bearer in the homozygous condition.
Are there any constraints on mutation?
No, anything can happen.
What are the 2 views of evolution with respect to mutation?
- Neo-Darwinist = gradual accumulation of advantageous mutations improve the fitness of an organism
- Catastrophist = macro-mutations occur in regulatory gene sequences causing a cascade of multiple changes on other genes.
In the Neo-Darwinist theory of evolution, what kind of magnitude does each mutation have?
A small effect on evolution.
Mutation rate can be studied in different ways. Give 3 examples.
- Per cell cycle
- Per generation
- Per chromosome
Describe the experiment in mice used to assess mutation rate in loci per generation based on visible phenotypes.
- The reference population are all females that are homozygous recessive for different coat colours
- Cross these to wild type males
- Progeny are expected to be heterozygous at the marker (coat colour) loci
- Any other visible phenotypes are assumed to be mutations.
Mutation rate at each locus is very low, so you would expect the affect of mutation on variation to be very small. Why is this not the case?
The number of mutations is summed across all the genes, meaning the input to variation is considerable.
Mutations are only ever advantageous, deleterious or lethal. True or false?
False - they can also be neutral.
Who performed the famous mutation experiment on drosophila in 1972?
Mukai.
What was the point of Mukai’s experiment in 1972?
He allowed the accumulation of slightly deleterious mutations over generations at multiple loci to assess their impact on fitness.