Gene pool
The total of all the alleles of all the genes in a population at a given time
Population genetics is not concerned with the genotypes of individuals, but describes the allele frequencies.
Define allele frequency
It is the allele’s proportion/fraction/percentage out of all the alleles of that gene in the gene pool.
Genetic drift
Chance variations in allele frequency in a population. Most significant in small or isolated populations when a small number of alleles form a large proportion of the total.
For example, in a very small population, it may be that, by chance, none of those possessing a certain allele mate with one another. Then the allele is lost from the population altogether!
Hardy-Weinberg principle
States that, in ideal conditions, allele and genotype frequencies are constant from generation to generation. There are 9 ideal conditions
The conditions of the Hardy-Weinberg principle
Organisms:
Are diploid
Allele frequencies are equal in both sexes
Reproduce sexually
Mating is random
Generations don’t overlap
Population:
Very large
No immigration/emigration
No mutation
No selection
Hardy-Weinberg equation
p² + 2pq + q² = 1
p is frequency of the DOMINANT allele
q is frequency of the RECESSIVE allele
thus:
p² is dominant homozygous frequency (e.g AA)
2pq is heterozygous frequency (Aa)
q² is recessive homozygous frequency (aa)
Under the 9 conditions of the HW principle, p and q frequencies remain constant so the population is said to be in..?
Hardy-Weinberg equilibrium