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In the species of violet Viola granulanica, the allele Y is responsible for pigmentation of the petals and the allele X is responsible for petal shape. The dominant allele Y creates a red pigmentation in the petals, and a homozygous recessive pair of this allele will result in blue petals. The dominant allele X creates pointed petals, and a homozygous recessive pair of this allele will result in rounded petals.
If a flower with the alleles YyXX and a flower with the alleles YyXx breed, what percent of the offspring will have blue-pointed petals?
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Correct Answer: B. 25%
The resulting progeny will have 4 violets with blue-pointed petals out of a total of 16 possible combinations. If we generate a Punnet Square, we can lay out the alleles in the genetic cross. As we can see, there are 16 combinations possible, 12 of which result in red-pointed petals and 4 of which result in blue-pointed petals.
There are no combinations featuring rounded petals, because the first flower did not contain any recessive alleles for X, and therefore all the resulting progeny in the cross have pointed petals.
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