Question

Colored aleurone in the kernels of corn is due to the dominant allele R. The recessive allele r, when homozygous, produces colorless aleurone. The plant color (not the kernel color) is controlled by another gene with two alleles, Y and y. The dominant Y allele results in green color, whereas the homozygous presence of the recessive yallele causes the plant to appear yellow. In a testcross between a plant of unknown genotype and phenotype and a plant that is homozygous recessive for both traits, the following progeny were obtained:Colored, green 88Colored, yellow 12Colorless, green 8Colorless, yellow 92Based on the data, what can you say about the genotype of the unknown plant?A. It was heterozygous for one gene, and homozygous for the other.B. It was homozygous for both genes.C. It was heterozygous for both genes.

Answer 1

Answer: C. It was heterozygous for both genes.

Explanation: To produce a generation that has individuals with trait for colored aleurone in the kernels, the plant being analised has to have a dominant allele R. In the same way, to have offspring with the recessive trait, it has to carry the recessive allele r. So, the unknown plant has to be heterozygous for colored aleurone in the kernels, Rr.

The same thought can be applied to plant color: Since there are green and yellow plants, the unknown plant has to be heterozygous for that trait, Yy.

In conclusion, the unknown plant is heterozygous for both genes.