Final answer:
Allele frequencies represent the relative frequency of a specific allele in a population, whereas genotype frequencies refer to the proportion of individuals with a particular combination of alleles. Predicting genotype frequencies from known allele frequencies can be done mathematically under Hardy-Weinberg equilibrium conditions. These concepts are crucial for understanding population genetics and evolutionary biology.
Step-by-step explanation:
Allele frequencies and genotype frequencies are related concepts, but they are not the same thing. Allele frequency refers to how often a specific allele occurs in a population, while genotype frequency is the rate at which a specific genotype (combination of alleles) occurs in that same population.
For instance, using the pea plant example where yellow peas are represented by allele Y and green peas by allele y, the allele frequency would refer to the proportion of Y alleles versus y alleles in the gene pool. If we know the allele frequencies, predicting genotype frequencies involves a simple mathematical model where p and q represent the frequencies of each allele (Y and y, respectively).
The genotype frequencies can be calculated assuming Hardy-Weinberg equilibrium conditions as: the frequency of homozygous dominant individuals (YY) is p², the frequency of heterozygous individuals (Yy) is 2pq, and the frequency of homozygous recessive individuals (yy) is q². These genotype frequencies will sum to one: p² + 2pq + q² = 1. This demonstrates that the genotype frequencies in the population can be expressed in terms of the two allele frequencies.
Changes in allele and genotype frequencies can indicate evolutionary pressures such as genetic drift, which is the effect of chance events on a population's genetic structure. Variations from expected Hardy-Weinberg frequencies can help scientists infer these evolutionary forces.