Population Genetics and Natural Selection Flashcards
What is a population?
Localised group of individuals of the same species
What is a gene pool?
Total aggregate of genes (and their alleles) in a population at one time
Why might we need to estimate frequencies of genotypes in a population?
To predict how many individuals will inherit a genetic disease
To estimate the proportion of individuals who are carries of a disease
How do we predict genotypes in a population?
Allele frequency : p + q = 1
Genotypic frequency : p^2 + 2pq + q^2 = 1
What is random genetic drift?
A random change in allele frequencies due to sampling error over generations
What is the bottleneck effect?
The bottleneck effect is an extreme example of genetic drift that happens when the size of a population is severely reduced due to natural disasters
What is founder effect?
The reduced genetic diversity which results when a population is descended from a small number of ancestors.
What is stabilising selection?
Phenotypes favoured by natural selection in middle so peak gets higher and narrower
Reduces variation but does not change the mean
What is directional selection?
Smaller or larger phenotype so peak shifts either left or right
Changes the mean value towards one extreme
What is disruptive selection?
Favours the two phenotypic extremes (highest extreme and lowest extreme) producing two peaks
What is sexual selection?
Sexually selected traits are those traits that help an organism reproduce by competing for and attracting a mate
What is frequency dependent selection?
A situation where fitness is dependent upon the frequency of a phenotype or genotype in a population
What is spatial distribution of genetic variation?
The gradual geographic change in genetic/phenotypic composition referred to as CLINE
What is a mutation?
Very slow to act and usually disadvantageous
Usually of macroevolutionary propotions
What is migration?
An individual from another population successfully mates to the gene pool bringing new alleles hence population size changes
