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
