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)a maternal age effect
B)a chromosomal aberration involving chromosome 1
C)an inversion involving chromosome 21
D)a translocation between chromosome 21 and a member of the D chromosome group
E)too many X chromosomes

Question

Quizplus · Accepted Answer

Familial Down syndrome can be caused by a translocation between chromosome 21 and a member of the D chromosome group. This can result in the offspring inheriting extra copies of genes on chromosome 21, leading to characteristics of Down syndrome.

Although the Most Frequent Forms of Down Syndrome Are Caused