In a population there are many
different phenotypes, proteins, and
alleles (DNA)
Allele frequencies vary from population to population
Africans have a high
frequency of the sickle
cell allele, Northern
Europeans have a high
frequency of the cystic
fibrosis allele, Ashkenazi
Jews have a high
frequency of the Tay
Sachs allele
Hardy-Weinberg Law
Frequencies of alleles
of the same gene will
remain the same from
generation to
generation provided:
that population is
infinitely large, mating is
random, selection is not
occurring, no mutation ,
no migration
Problem: populations vary in size
Genetic Drift
Random changes in
gene frequencies due
to chance; seen in
small populations
Causes
Size is small over a
long period of time
Founder Effect
Bottleneck Effect
Genetic bottleneck:
some genotypes do
not survive
Problem: there are many
situations where mating is not
random