Define fitness

means the relative ability of organisms to survive and pass on genes

What effects fitness

alleles

What do genotype frequencies calculate

How many genotypes in the population

How do we calculate genotype frequency

the number of people with that genotype divided by the number of people overall

What must an allele frequency always add up to

1

What is the genotype frequency equation for

AA : Aa : aa

p2 : 2pq : q2

What is the allele frequency of A:a

p:q

What do the allele frequency and genotype frequency of the Hardy-Weinberg equilibrium prove to us

Relative frequencies always remain constant therefore dominant alleles don’t become more common

What is an idea population that will fit withHardy-Weinberg equilibrium

Mutation can be ignored Migration is negligible (No gene flow) Mating is random No selective pressure Population size is large Allele frequencies are equal in the sexes

What can increases the proportion of new alleles

Mutations

Migrations

What can increase mutant alleles

Non random mating

What are two forms of nonrandom mating

Assortative mating - of shared characteristics

Consanguinity - between relatives

Define natural selection

A gradual process by which biological traits become either more or less common in a population

What natural selection increases reproductive fitness the prevalence of adaptive traits and it gives a heterozygote advantage

Postive selection

What does negative selection reduce

reproductive fitness

prevalence of traits

reduction of mutant allele

Give 3 examples of heterozygous advantages and there resistances

sickle cell anaemia - malaria

cystic fibrosis - cholera/typhoid

Glucose 6 phosphate dehydrogenase deficiency - malaria

What can small population cause

genetic drift

founder effect

Define genetic drift

Statistical drift of gene frequencies due to chance or random events leading to the variation in the relative frequency of different genotypes in a small population

Define founder effect

The reduction in genetic variation that results when a small subset of a large population is used to establish a new colony

What is the result of the founder effect

limits genetic variation

What is applications of HWE

Useful for calculating risk in genetic counselling

Useful for planning population based carrier screening programmes

To calculate a carrier frequency what do you need to find out of ratio p² : 2pq : q²

2pq - heterozygote

How do you work out carrier frequency,

well you calculate q from statistic p+q= 1, calculate p= 1-q, Now you have p and q 2 x p x q =2pq