Question

How many chromosomes are there in a somatic cell of a person with Down syndrome (trisomy of chromosome 21)?

A) 46 chromosomes; 22 autosomes.
B) 47 chromosomes; 23 autosomes.
C) 48 chromosomes; 24 autosomes.
D) 45 chromosomes; 21 autosomes.

Answer 1

A person with Down syndrome has trisomy of chromosome 21, resulting in 47 chromosomes in their somatic cells. The correct answer is option B) 47 chromosomes; 23 autosomes.

Step-by-step explanation:

A person with Down syndrome has trisomy of chromosome 21, which means they have an extra copy of chromosome 21. Therefore, the correct answer is option B) 47 chromosomes; 23 autosomes. In a somatic cell of a person with Down syndrome, there are 47 chromosomes instead of the usual 46.