What is heterozygosity and why is it useful?

• A. Proportion of individuals that are homozygous at a locus; reflects inbreeding levels
• B. Proportion of individuals that are heterozygous at a locus; reflects genetic diversity and potential for adaptation
• C. Average number of mutations per genome
• D. Proportion of alleles that are fixed

Answer: (B)

Heterozygosity is a measure of genetic variation within a population, defined as the proportion of individuals that carry two different alleles at a given locus (or the likelihood that two alleles drawn at random form a heterozygote). This reflects how diverse the genetic material is.

Why it’s useful: more heterozygosity means more raw material for natural selection to act on, giving populations greater potential to adapt to changing environments, diseases, or other pressures. It also helps reduce the risks of inbreeding depression by maintaining allelic diversity.

For context, the other ideas describe different things: a high proportion of homozygotes points to inbreeding or loss of variation; the average number of mutations per genome is a mutation-rate concept; and a high proportion of fixed alleles means little to no variation at that locus.