Question

white feathers in canaries are dominant to yellow feathers. a heterozygous canary is crossed with a homozygous recessive canary. what is the ratio of the offspring that are homozygous to the total number of offspring? what percent of the offspring will be heterozygous?

Explanation:

Step1: Set up the cross

Let the dominant allele for white feathers be \(A\) and the recessive allele for yellow feathers be \(a\). The heterozygous canary has the genotype \(Aa\) and the homozygous - recessive canary has the genotype \(aa\).

Step2: Create the Punnett - square

The possible gametes of the heterozygous canary (\(Aa\)) are \(A\) and \(a\), and the possible gametes of the homozygous - recessive canary (\(aa\)) are \(a\) and \(a\). The Punnett - square shows the following genotypes of the offspring: \(Aa\), \(Aa\), \(aa\), \(aa\).

Step3: Calculate the ratio of homozygous offspring

The homozygous offspring have the genotype \(aa\). There are 2 homozygous offspring out of a total of 4 offspring. The ratio of homozygous offspring to the total number of offspring is \(\frac{2}{4}=\frac{1}{2}\).

Step4: Calculate the percentage of heterozygous offspring

The heterozygous offspring have the genotype \(Aa\). There are 2 heterozygous offspring out of a total of 4 offspring. The percentage of heterozygous offspring is \(\frac{2}{4}\times100\% = 50\%\).

Answer:

1. \(\frac{1}{2}\)
2. \(50\)