Although the most frequent forms of Down syndrome are caused by a random error,nondisjunction of chromosome 21,Down syndrome occasionally runs in families.The cause of this form of familial Down syndrome is ________.
A) an inversion involving chromosome 21
B) a chromosomal aberration involving chromosome 1
C) too many X chromosomes
D) a translocation between chromosome 21 and a member of the D chromosome group
E) a maternal age effect

Question

Quizplus · Accepted Answer

Familial Down syndrome is caused by a translocation between chromosome 21 and a member of the D chromosome group. This results in some of the genetic material from chromosome 21 being attached to another chromosome, which can lead to the characteristic features of Down syndrome.

Although the Most Frequent Forms of Down Syndrome Are Caused