Question

In maize, the dominant allele b-i encodes a transcription factor that regulates genes involved in producing the purple color of corn stalks and husks. The allele can undergo a mutation to b' which changes the stalk and husk color from purple to green. In a cross between b-i b-i and b' b' homozygotes, the F1 heterozygotes all have green stalks and husks. This shows that the b' allele is:

A) Recessive
B) Codominant
C) Dominant
D) Incomplete Dominant

Answer 1

Answer: The most appropriate answer is C) Dominant, as the b' allele is capable of expressing its phenotype (green color) when present alongside the b-i allele.

Step-by-step explanation:

In the given scenario, the dominant allele b-i encodes a transcription factor that regulates genes involved in producing the purple color of corn stalks and husks. This means that the presence of the b-i allele results in the production of the purple color.

On the other hand, the b' allele is a mutation of the b-i allele, which changes the stalk and husk color from purple to green. This suggests that the presence of the b' allele overrides the production of the purple color and instead leads to the production of the green color.

In the cross between b-i b-i and b' b' homozygotes, where both parents carry two copies of either the b-i or b' allele, all the F1 heterozygotes (b-i b') exhibit green stalks and husks. This indicates that the b' allele is dominant over the b-i allele, as it determines the color phenotype in the presence of both alleles.