Download Hardy Weinberg Equilibrium and Evolution

Hardy Weinberg Equilibrium and
Evolution
SC.912.L.15.12
Microevolution
• A key concept in understanding the
evolution of populations is the gene pool
• Gene pool: consists of all the alleles
(alternative forms of genes) in all the
individuals that make up a population
– think of the gene pool as the reservoir from
which the next generation draws its genes
– the population's gene pool is where genetic
variation—the raw material of evolution—is
stored
Microevolution
• Microevolution: evolution on the smallest scalea generation to generation change in the
frequencies of alleles within a population
• Hardy Weinberg Equilibrium: populations that
do not undergo change to their gene pools are
not presently evolving
– frequency of alleles in that gene pool are constant over
time
– useful because it provides a "no change" baseline that
makes it possible to recognize when a gene pool is
changing
Hardy-Weinberg Principle
• Necessary assumptions
Allelic frequencies would remain constant if…
– population size is very large
– random mating
– no mutation
– no gene input from external sources
– no selection occurring
Hardy-Weinberg Principle
• Calculate genotype frequencies with a binomial
expansion
(p+q)2 = p2 + 2pq + q2
• p2 = individuals homozygous for first allele
• 2pq = individuals heterozygous for alleles
• q2 = individuals homozygous for second allele