Question

The white color of the squash is controlled by a dominant gene (W), and green is the recessive allele. And the yellow fruit is controlled by a hypostatic gene, Free segregation (G) and green with a recessive allele. If two dihybrid plants pollinate each other, A- What are the phenotypic ratios in the resulting offspring?

Answer 1

The phenotypic ratio resulting from a cross of two heterozygous summer squash plants (WwYy) is 12 white, 3 yellow, and 1 green. This is due to epistasis, where the presence of a dominant W allele masks the expression of the Y gene, leading to white squash unless both genes are homozygous recessive.

Step-by-step explanation:

Phenotypic Ratios in Dihybrid Crosses

The concept in question is known as epistasis, which occurs in genetics when the expression of one gene is affected by another. In the case of summer squash, the color is determined by two genes with the following dominant and recessive alleles: The W gene, where dominant W results in white squash, and the Y gene, which contributes to the yellow color when the W gene is homozygous recessive (ww). Green squash results from the recessive expression of both genes (wwyy).

When two heterozygous plants (WwYy x WwYy) are crossed, we can anticipate the offspring to have a phenotypic ratio of 12 white:3 yellow:1 green. This ratio arises because the W gene is epistatic to the Y gene; the presence of at least one dominant W allele (Ww or WW) will mask the expression of the Y gene, leading to white fruit. Consequently, yellow fruit is only produced when the W gene is homozygous recessive (ww) coupled with at least one dominant allele of the Y gene (Yy or YY). When both ww and yy genotypes are present, green fruit is produced.