Genetic variation in populations can be analyzed and quantified by the frequency of alleles.
Although allele and genotype frequencies are related, it is important to clearly distinguish them.
Genotype frequency may also be used in the future (for "genomic profiling") to predict someone's having a disease[3] or even a birth defect.
As an example, consider a population of 100 four-o-'clock plants (Mirabilis jalapa) with the following genotypes: When calculating an allele frequency for a diploid species, remember that homozygous individuals have two copies of an allele, whereas heterozygotes have only one.
The Hardy–Weinberg law describes the relationship between allele and genotype frequencies when a population is not evolving.