Final answer:
Allele frequency is the most frequently used measure of genetic variation, with recombination frequency helping to determine genetic distances on chromosomes, often measured in centimorgans.
Step-by-step explanation:
The most frequently used measure of genetic variation is allele frequency, which is how often an allele occurs in a gene pool relative to the other alleles for that gene. In population genetics, evolution is characterized as a change in an allele's frequency within a population. Scientists use recombination frequency, which correlates with genetic distance, as a quantitative measure to predict the relative order of genes on a chromosome. Genetic distances are often represented in centimorgans (cM), and a recombination frequency of 1% correlates with a genetic distance of 1 cM, facilitating the construction of genetic maps.