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Modern Genetic Analysis
17. Population and Evolutionary Genetics
Key Concepts

The goal of population genetics is to understand the genetic composition of a population and the forces that determine and change that composition.
In any species, a great deal of genetic variation within and between populations arises from the existence of various alleles at different gene loci.
A fundamental measurement in population genetics is the frequency at which the alleles are found at any gene locus of interest.
The frequency of a given allele in a population can be changed by recurrent mutation, selection, or migration or by random sampling effects.
In an idealized population, in which no forces of change are acting, a randomly interbreeding population would show constant genotypic frequencies for a given locus.

Mendel's investigations of heredityindeed all the interest in heredity in the nineteenth centuryarose from two related problems: how to breed improved crops and how to understand the nature and origin of species. What is common to these problems (and differentiates them from the problems of transmission and gene action) is that they are concerned with populations rather than with individuals. Studies of gene replication, protein synthesis, development, and chromosome movement focus on processes that go on within the cells of individual organisms. But the transformation of a species, either in the natural course of evolution or by the deliberate intervention of human beings, is a change in the properties of a collectivityof an entire population or a set of populations.

MESSAGE
Population genetics relates the heritable changes in populations of organisms to the underlying individual processes of inheritance and development.

© 1999 by W. H. Freeman and Company. All rights reserved.