Suppose members of a true-breeding strain of salamanders with yellow stripes are crossed with a true-breeding strain with red stripes.Red and yellow are two alleles of the same gene.The resulting offspring have both yellow stripes and red stripes.What pattern would you expect in the F₂ generation? A) Half will have yellow stripes, and half will have red stripes. B) Half will have both yellow and red stripes, one-quarter will have just yellow stripes, and one-quarter will have just red stripes. C) One-third will have both yellow and red stripes, one-third will have just yellow stripes, and one-third will have just red stripes. D) Half will have both yellow and red stripes, and half will be stripeless. E) One-quarter will have both yellow and red stripes, half will have just yellow stripes, and one-quarter will have just red stripes.

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Quizplus · Accepted Answer

The pattern described suggests that the alleles for yellow and red stripes are codominant, meaning both traits are fully expressed in heterozygotes. In the F2 generation, following Mendelian genetics, we expect a 1:2:1 phenotypic ratio for a monohybrid cross involving codominant traits: one-quarter will be homozygous for one trait (yellow), one-quarter homozygous for the other trait (red), and half will be heterozygous expressing both traits (yellow and red stripes).

Suppose Members of a True-Breeding Strain of Salamanders with Yellow