White fruit color in summer squash is influenced by a dominant allele W,whereas colored fruit must be ww.In the presence of ww,a dominant gene G results in yellow fruit,and homozygous gg results in green fruit.The F2 phenotypic ratios resulting from a cross of a true-breeding plant with white fruit (genotype WW GG)with a plant with green fruit will result in which phenotypic ratios?
A) 8/16 white, 4/16 yellow, 4/16 green
B) 12/16 white, 3/16 yellow, 1/16 green
C) 4/16 white, 8/16 yellow, 4/16 green
D) 12/16 white, 2/16 yellow, 2/16 green
E) 8/16 white, 8/16 green

Question

White fruit color in summer squash is influenced by a dominant allele W,whereas colored fruit must be ww.In the presence of ww,a dominant gene G results in yellow fruit,and homozygous gg results in green fruit.The F2 phenotypic ratios resulting from a cross of a true-breeding plant with white fruit (genotype WW GG)with a plant with green fruit will result in which phenotypic ratios?  
A) 8/16 white, 4/16 yellow, 4/16 green
B) 12/16 white, 3/16 yellow, 1/16 green
C) 4/16 white, 8/16 yellow, 4/16 green
D) 12/16 white, 2/16 yellow, 2/16 green
E) 8/16 white, 8/16 green

Quizplus · Accepted Answer

The true-breeding plant with white fruit (WW GG) can only produce gametes with W and G alleles. The plant with green fruit must be homozygous for the recessive w allele (ww gg) and can only produce gametes with w and g alleles. 
Therefore, the F1 offspring will all be heterozygous (Ww Gg) for both traits and will have white fruit. 
When these F1 offspring are crossed, the expected phenotypic ratio in the F2 generation is 9:3:3:1 for white-yellow-green. 
However, we have to remember that the green fruit trait is recessive and only appears when an individual is homozygous for the gg genotype. 
Therefore, out of the 16 total possible offspring, there will only be 1 that is green (gg ww), while the remaining 15 offspring will have at least one dominant allele and have white or yellow fruit. 
The most likely outcome is 12/16 white, 3/16 yellow, and 1/16 green.

White Fruit Color in Summer Squash Is Influenced by a Dominant