Question

What percentage of offspring from a cross between a homozygous type A parent with a heterozygous Type A parent is expected to contain the I allele


a)100%

b)50%

c)75%

d)25%

Answer 1

The correct answer is option B, 50%

Let us take the following case:

Genotype of heterozygous parent - (Aa)

Genotype of homozygous parent – (aa)

Allele I  - (Aa)

Allele II – (aa)

The cross between the two is shown below:

Aa  X aa

Aa, Aa, aa, aa

There are 50 % Aa, and 50 % aa allele.  

Thus, the allele I (Aa) is 50 %.