## V.3 The probability of an allele becoming fixed by drift is determined by its original frequency in the population.

The processes of *fixation of alleles* through the action of *genetic drift* are random from the standpoint of the moment when they occur and also to a substantial degree from the standpoint of which of the alleles will be *fixed* in the given population and which will be eliminated.The probability that the individual alleles will be fixed or eliminated differs for these individual alleles.For most alleles, these probabilities depend primarily and, in many alleles, exclusively on their momentary frequency in the population.If the population contains two alleles with the same frequency, then they both have the same probability of becoming fixed in the population.If the frequency of one of the alleles is, for example, ten times greater, then it also has ten times the probability of becoming fixed.If a population of organisms containing allele **A** with a frequency of 0.9 and allele **a** with a frequency of 0.1 is divided into one hundred smaller populations, then, after a sufficiently long period of time, allele **A** will become fixed in approximately 90 of them and allele **a** in approximately 10.