In genetics, what does "allele frequency" refer to?

Allele frequency refers to the proportion of a specific allele within a population, which is crucial for understanding genetic diversity and evolution within that population. It is calculated by taking the number of times a particular allele appears in a population and dividing it by the total number of alleles for that gene present in the population. This measurement helps geneticists and ecologists study how common or rare a particular allele is, assess the genetic variation of populations, and understand evolutionary processes, such as natural selection or genetic drift.

In contrast, the other options touch on different aspects of genetics but do not define allele frequency accurately. The number of genes in an organism refers to the total genetic information rather than the frequency of specific variations. The total number of alleles in a genome does not specify which allele is being referenced. Lastly, the predictability of genetic mutations addresses changes in DNA over time rather than focusing on the presence or absence of specific alleles in a population. Thus, option B correctly captures the essential concept of allele frequency.