Question

Brown eyes are dominant over blue eyes. If two brown eyed parents have a child with blue eyes, what does it mean about

parent's genotype?
•
A. They must both be homozygous dominant.
•
B. One must be heterozygous.
• °C. They must both be heterozygous.
•
D. One must be homozygous recessive.

Answer 1

The answer is D.

Answer 2

°C. They must both be heterozygous.

Explanation: For a brown eyes parents to give birth to a blue eyes offspring it means the both parents are heterozygous.

Since D is for dominant allele and

d is for recessive allele

DD is for Homozygous individual (i.e) dominant gene

Dd is for heterozygous individual

dd is for homozygous recessive individual

Dd ×Dd- parents

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DD Dd Dd dd - offsrings 1:2:1

DD- 1 brown eye homozygous offspring

Dd- 2 brown eye heterozygous offspring

dd- 1 blue eye homozygous individual

A cross between two heterozygous individual will lead to segregation of genes in the ratio 1:2:1 i.e 3 brown and 1 blue eye individual.