Question

Which type of chromosome mutation is responsible for familial Down syndrome?

a) Deletion
b) Duplication
c) Inversion
d) Translocation

Answer 1

Familial Down syndrome is typically caused by a translocation mutation, often involving chromosome 21 and another chromosome. This is different from the more common trisomy 21, which results from nondisjunction during meiosis.

Step-by-step explanation:

The type of chromosome mutation responsible for familial Down syndrome is translocation. This occurs when a segment of one chromosome breaks off and attaches itself to a different chromosome. Familial Down syndrome is often associated with a translocation between chromosome 21 and another chromosome, leading to an inheritable form of Down syndrome when the offspring inherits the translocated chromosome.

In most cases, Down syndrome is caused by trisomy 21, which is the presence of three copies of chromosome 21. This is usually due to nondisjunction during meiosis, where chromosome 21 fails to separate properly, leading to a gamete with an extra copy of this chromosome.