Question

If Down Syndrome is cause by nondisjunction, what is the source of familial Down syndrome?

A) Inherited chromosomal translocations
B) Environmental factors during pregnancy
C) Genetic mutations in DNA repair enzymes
D) Inherited predisposition to chromosomal nondisjunction

Answer 1

Familial Down syndrome is caused by inherited chromosomal translocations, where a segment of chromosome 21 attaches to another chromosome and can be passed down from parent to child.

Step-by-step explanation:

The source of familial Down syndrome is A) Inherited chromosomal translocations. This type of Down syndrome occurs when a segment of chromosome 21 becomes attached, or translocated, to another chromosome during cell division. Familial Down syndrome is less common than the Down syndrome caused by nondisjunction, which is the most familiar cause and arises from a failure of chromosome 21 pairs to separate properly during meiosis, leading to an embryo with three copies of chromosome 21 instead of the usual two. Translocation Down syndrome is inherited when a parent carries a translocated chromosome that can be passed down to a child, leading to an effectively trisomic chromosome 21 condition.