Question

In a human genetic study, a family with five phenotypically normal children was investigated. Two children were "homozygous" for a Robertsonian translocation between chromosomes 19 and 20 (they contained two identical copies of the fused chromosome). They have only 44 chromosomes but a complete genetic complement. Three of the children were "heterozygous" for the translocation and contained 45 chromosomes, with one translocated chromosome plus a normal copy of both chromosomes 19 and 20. Two other pregnancies resulted in stillbirths. It was later discovered that the parents were first cousins.

Part A

What are the chromosome compositions of the parents?

Select the four correct compositions.

Select the four correct compositions.

Each parent has Robertsonian t(19;20).

One parent has Robertsonian t(19;20).

Each parent is homozygous for the translocation.

Each parent is heterozygous for the translocation.

One parent is heterozygous for the translocation.

Each parent has normal chromosome 19.

Each parent has normal chromosome 20.

One parent has normal chromosome 19.

One parent has normal chromosome 20

Answer 1

here there are 2 children who are homozygous for the translocation so both parents should have at least one chromosome with translocation, and there are 2 children who are heterozygous and there are 2 stillbirths, stillbirths arise due to monosomy of chromosome 19 or 21, means those lack one copy of chromosome 21 or 19, this arises when both parents are heterozygous

so the answers are

Each parent has Robertsonian t(19;20).

Each parent is heterozygous for the translocation

Each parent has normal chromosome 20.

Each parent has normal chromosome 19.