Inbreeding has two important effects Inbreeding increases homozygosity at many genes inbreeding depression . MM MN NN Total Pop. Other points about gene flow from an evolutionary standpoint. Gene flow is an important source of genetic variation in populations Gene flow between populations is a homogenizing force The third evolutionary force is mutation . The fourth evolutionary force is called genetic drift .
Genetic drift is defined as the random sampling error of gametes .
First consider random sampling error in general. The answer is of course 0.5 heads and 0.5 tails. While the theoretical expectations are 5 and 5, random sampling error can cause departures from these expectations. In small populations, allele and genotype frequencies may change and differ from our expected frequencies by random sampling error freqs. It is a random process, drift in several different populations may cause them to diverge genetically Historical events may also cause changes and loss of variation by drift.