92 I The Process of Evolution 



of the type of the male participant and the frequency of the type of 

 his female partner. For example, consider a hypothetical animal 

 which has both black and white forms and exists in a panmictic 

 population consisting of 100 males (90 black, 10 white) and 100 

 females ( 70 black, 30 white ) . The expected frequencies of the vari- 

 ous matings are given in Table 6.1. 



Statistical study of the frequencies of the various matings might 

 show that observed deviations from these expected frequencies are 

 satisfactorily explained by sampling error (i.e., chance), leading to 

 the conclusion that, at least with respect to color, the population was 

 panmictic. To look at panmixis another way, it can be said to occur 

 when the genotypes of the individuals in each mating pair are a 

 random sample of the genotypes present in the population. Complete 

 panmixis seems rare or nonexistent in nature, if for no other reason 

 than that relatives often tend to live close together and thus mate 

 with one another. When this happens, the mating pairs are not a 

 random selection from the population, and a component of inbreed- 

 ing is added to the population-genetic picture. 



Gene Pool and Gene Frequency 



The total genetic information possessed by a population may be 

 referred to as the gene pool of the population. If the gene pool could 

 be described completely, one would know not only what kinds of 

 information were present but also the frequencies of the different 

 kinds. This chapter is concerned mostly with the distribution within 

 the gene pool of the information at a single locus. 



One of the basic ideas of population genetics is that of gene fre- 

 quency. If it is assumed that there are only two alleles at the locus 

 {A,a) under consideration, there are then N diploid individuals of 

 which D are homozygous for one allele (AA) with respect to the 



Table 6.1 



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