In foxes, two alleles of a single gene, P and p, may result in lethality (PP), platinum coat (Pp), or silver coat (pp). What ratio is obtained when platinum foxes are interbred? Is the P allele behaving dominantly or recessively in causing (a) lethality; (b) platinum coat color?

Key Concepts

Alleles and Genotypes

Alleles are different versions of a gene that can exist at a specific locus on a chromosome. In this case, the alleles P and p represent two variations of a gene affecting coat color in foxes. The genotype of an organism, which is the combination of alleles it possesses (e.g., PP, Pp, pp), determines its phenotype, or observable traits, such as coat color and lethality.

Dominance and Recessiveness

Dominance refers to the relationship between alleles where one allele masks the expression of another. In this scenario, the P allele is dominant over the p allele in determining coat color, as Pp results in a platinum coat. However, the P allele is also associated with lethality when homozygous (PP), indicating that its effects can vary depending on the context of the genotype.

Punnett Squares and Genetic Ratios

A Punnett square is a tool used to predict the genotypic and phenotypic ratios of offspring from a genetic cross. When interbreeding platinum foxes (Pp x Pp), the Punnett square reveals the expected ratios of offspring: 1 PP (lethal), 2 Pp (platinum), and 1 pp (silver), resulting in a 2:1 ratio of platinum to silver foxes, with no viable PP offspring.