Question

In wheat plants, the feature of having colored kernels is dominant to having white kernels that lack pigment. A true-breeding plant with colored kernels is crossed to a true-breeding plant with white kernels, resulting in progeny that all harbor colored kernels. The F1 progeny are then crossed, and a few members of the F2 generation have white/colorless kernels. The modified ratio observed is 15 colored: 1 non-colored. Explain these results.

Answer 1

Answer: It occurred a dihybrid cross and epistasis.

Explanation: In dihybrid cross, two different genes controlled two different traits. When they interact with each other is called Epistasis. However, in wheat plants, the genes related to color kernels don't act opposedly to each other. In other words, the genes have the same role in producing protein, so they can substitute for each other.

In the color determination mechanism, a biochemical reaction is necessary to convert a precursor substance into a pigment and that reaction happens with the product of either genes. That's why having a dominant allele makes the wheat colorful. So, crossing colored kernels with white ones will produce a heterozygous F1 generation. Crossing this generation will produce a F2 generation with modified ratio of 15 colored: 1 non colored because, every individual who has  dominant alleles will produce the substance and thus the biochemical reaction will happen. Only recessive homozygous ones won't have the substance and so won't have color.