Question

Summer squash plants with the dominant allele C bear white fruit, whereas plants homozygous for the recessive allele c bear colored fruit. When the fruit is colored, the dominant allele G causes it to be yellow; in the absence of this allele (that is, with genotype gg), the fruit color is green. What are the phenotypes and proportions expected from intercrossing the progeny of CC GG and cc gg plants? Assume that the C and G genes assort independently.

Answer 1

Answer:

12 white: 3 Yellow: 1 Green

Explanation:

Fruit color inheritance in Summer Squash is an example of dominant epistasis wherein a dominant allele masks the expression of both dominant and recessive alleles present at some other locus.  

Here, the allele "C" is epistatic to G and g alleles and masks their expression. Hence, the F2 progeny with genotypes C-G- and C-gg bear white fruits. In absence of dominant allele "C", the genotype "cc-G-" gives yellow fruit color while the genotype "ccgg" imparts green fruit color.  

Therefore, the F2 progeny obtained from crossing the F1 dihybrid from the parents "CCGG" and "ccgg" exhibits the following phenotype ratio=

12 white : 3 yellow: 1 green