1. On a fox ranch in Wisconsin, a mutation arose that gave a platinum coat color

Question

1. On a fox ranch in Wisconsin, a mutation arose that gave a platinum coat color. The platinum coat color proved very popular with buyers of fox coats, but the ranchers could not develop a pure breeding platinum strain. Every time they bred two platinum foxes some of the progeny were always red. For example one repeated mating of two platinum foxes produced 82 platinum and 32 red foxes, Similar matings always produced similar results. Explain the genetic phenomena which could cause all mating between platinum foxes to generate this type of phenotypic ratio.

Explanation / Answer

Ans-according to the question ranchers cannot develop a pure- breeding platinum strain and it must be dominant to red color and heterozygous (P/p).

Pp x Pp both parents produce P and p gametes in equal proportion which combine to give PP Pp pP and pp offspring, so you expect a ratio of 3:1 platinum:red.

Two platinums produced 82 platinum and 32 red normal progeny I. e. 82:32 which is very close to 2:1.This shows that it is a part of the heterozygous (P/p) ratio (1:2:1) in which one genotype is non-viable (P/P-homozygous platinum), because the homozygous recessive genotype is normal color (p/p), Therefore, the platinum allele is a pleiotropic allele ( where one gene affects multiple characteristics) that governs coat color in the heterozygous state (P/p) and is lethal in the homozygous recessive state.(P/P).

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