In humans the presence of chin and cheek dimples is dominant to the absence of dimples, and the ability to taste the compound PTC is dominant to the inability to taste the compound. Both traits are autosomal, and they are unlinked. The frequencies of alleles for dimples are D = 0.62 and d = 0.38. For tasting, the allele frequencies are T = 0.76 and t = 0.24. What are the expected frequencies of the four possible phenotype combinations: dimpled tasters, undimpled tasters, dimpled nontasters, and undimpled nontasters?

Key Concepts

Mendelian Genetics

Mendelian genetics is the study of how traits are inherited through generations based on the principles established by Gregor Mendel. It involves understanding dominant and recessive alleles, where dominant traits mask the expression of recessive ones. In this context, the presence of dimples and the ability to taste PTC are both dominant traits, which means individuals with at least one dominant allele will express these traits.

Hardy-Weinberg Principle

The Hardy-Weinberg principle provides a mathematical framework for understanding allele frequencies in a population at equilibrium. It states that allele and genotype frequencies will remain constant from generation to generation in the absence of evolutionary influences. This principle is essential for calculating expected genotype frequencies based on given allele frequencies, as seen in the question regarding dimples and tasting ability.

Phenotypic Ratios

Phenotypic ratios describe the relative frequencies of different phenotypes in a population resulting from genetic combinations. In this scenario, the expected phenotypic combinations arise from the interaction of two traits, each with dominant and recessive alleles. By applying the allele frequencies and the principles of independent assortment, one can calculate the expected frequencies of the four phenotype combinations: dimpled tasters, undimpled tasters, dimpled nontasters, and undimpled nontasters.