Punnett squares are used to show possible combinations of alleles or to predict the probability of a trait occurring in offspring. A parakeet that is heterozygous for blue feathers (dominant) is crossed with a parakeet that is homozygous for white feathers (recessive).
According to the Punnett square for this cross, what percentage of offspring is predicted to have blue feathers?

50 %

Explanation:

Hi there,

To get started, first determine an arbitrary letter for the allele. I chose the letter f for feathers. We know it is standard in genetics to use capital letter to indicate the dominant allele, and lowercase letter for recessive allele.

F - dominant     f - recessive

We now determine the following:

The parakeet crossing is between F/f x f/f.

Draw a Punnet Square.

When done, you should get two possible zygotes TWICE:

The question asks for offspring percentage to have BLUE feathers, which are the heterozygotes F/f. Since there are two offspring with this genotype for every four offspring, the ratio is:

2 offspring/ 4 offspring = 1/2 or 0.5

Convert to percentage by multiplying by 100%:

0.5 * 100% = 50%

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