Final answer:
Penetrance is the term that refers to the percentage of a population with a specific genotype that exhibits the expected phenotype. It indicates how often the presence of a gene leads to a phenotype, which is critical for understanding the genetic structure and evolution of populations.
Step-by-step explanation:
The term that refers to the percentage of a population with a particular genotype that exhibits the expected phenotype is penetrance.
Penetrance is used in genetics to describe the proportion of individuals carrying a particular genotype that also expresses an associated phenotype. For example, in a population with an allele frequency for a gene, we might find that not all individuals with a dominant allele display the dominant trait due to factors like incomplete penetrance. Population genetics studies the relationship between genotype frequency and phenotype expression by using equations that incorporate allele frequencies, such as the Hardy-Weinberg principle (p² + 2pq+q² = 1), to predict the expected phenotype distributions in a population.
Changes in allele frequency, such as the frequency of IA in the ABO blood type system, are critical to understanding evolution as they are behind changes in phenotype frequency, which can be calculated if the allele frequencies are known.