Question

This pedigree chart tracks the inheritance of a recessive trait that is not sex-linked. Based on the information in the chart, which of the following statements is true about individuals 3 and 4?

Answer 1

They are both heterozygous for the trait.

The reason why is because the child was born with a trait that only occurs by being homozygous recessive.

Answer 2

The correct answer is the third one: They are both heterozygous for the trait

If dominant allele: A
If recessive allele: a

A heterozygotic person has this genotype: Aa
A homozygotic dominant person has this genotype: AA
A homozygotic recessive person has this genotype: aa

They need to be both heterozygotic (Aa x Aa) for them to have a daughter who is recessive, while NOT having the trait themselves. By crossing their genotypes, there is 25% chance for them to have someone recessive for the trait (which they do, it's the daughter #10).