Question

Individuals with familial Down syndrome have how many chromosomes in each cell?

a)45
b)69
c)47
d)46
e)70

Answer 1

Individuals with familial Down syndrome have 47 chromosomes in each cell, with the extra chromosome being an additional copy of chromosome 21, leading to Trisomy 21.

Step-by-step explanation:

Individuals with familial Down syndrome typically have 47 chromosomes in each cell. This condition, also known as Trisomy 21, is caused by the presence of an extra copy of chromosome 21. Normally, humans have 46 chromosomes in each somatic cell, including two copies of chromosome 21, one inherited from each parent. In the case of Down syndrome, nondisjunction during meiosis results in a gamete with an extra chromosome 21, which, when fertilized, leads to a zygote with three copies of this chromosome. Thus, people with Down syndrome have a total of 47 chromosomes, which is a type of aneuploidy, specifically a trisomy.