the african cheetah.
this species has a relatively low level of genetic
variation because the population was reduced to a small size approxi-
mately 10,000 to 12,000 years ago.
chapter outline
24.1
genes in populations and the hardy-
weinberg equation
24.2
factors that change allele and genotype
frequencies in populations
24.3 sources of new genetic variation
population genetics
24
until now, we have primarily focused our attention on genes
within individuals and their related family members. in this
chapter and chapters 25 and 26 , we turn to the study of genes in
a population or species. the field of
population genetics
is con-
cerned with changes in genetic variation within a group of indi-
viduals over time. population geneticists want to know the extent
of genetic variation within populations, why it exists, and how it
changes over the course of many generations. the field of popu-
lation genetics emerged as a branch of genetics in the 1920s and
1930s. its mathematical foundations were developed by theoreti-
cians who extended the principles of gregor mendel and charles
darwin by deriving formulas to explain the occurrence of geno-
types within populations. these foundations can be largely attrib-
uted to three scientists: sir ronald fisher, sewall wright, and j. b. s.
haldane. as we will see, support for their mathematical theories
was provided by several researchers who analyzed the genetic com-
position of natural and experimental populations. more recently,
population geneticists have used techniques to probe genetic
variation at the molecular level. in addition, staggering advances
in computer technology have aided population geneticists in the
analysis of their genetic theories and data. in this chapter, we will
explore the genetic variation that occurs in populations and con-
sider the reasons why the genetic composition of populations may
change over the course of several generations
