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?

Verified step by step guidance

1. Identify the genotypes and their associated phenotypes: PP results in lethality, Pp results in platinum coat, and pp results in silver coat.
2. Set up a Punnett square for the cross between two platinum foxes, both with genotype Pp.
3. Fill in the Punnett square to find the genotypic ratios of the offspring: PP, Pp, and pp.
4. Translate the genotypic ratios into phenotypic ratios, considering that PP individuals are lethal and will not survive.
5. Analyze the phenotypic outcomes to determine if the P allele is dominant or recessive for (a) lethality and (b) platinum coat color by observing which phenotypes appear in heterozygotes.

Key Concepts

Mendelian Inheritance and Allele Interactions

Mendelian inheritance describes how alleles segregate and assort during reproduction, producing predictable genotype and phenotype ratios. Understanding dominant, recessive, and lethal alleles helps explain how different allele combinations affect traits and survival, such as when homozygous genotypes cause lethality.

Lethal Alleles and Their Effects

Lethal alleles cause death when present in certain genotypes, often homozygous. They reduce or eliminate specific genotypes from offspring ratios, altering expected Mendelian ratios. Recognizing lethality is crucial to interpreting deviations in phenotypic ratios from typical dominant-recessive patterns.

Dominance Relationships in Phenotypic Expression

Dominance refers to how one allele masks the effect of another in heterozygotes. An allele is dominant if it determines the phenotype when present, and recessive if its effect appears only in homozygotes. Determining dominance for traits like coat color or lethality involves analyzing offspring phenotypes from specific crosses.