Question

how many chromosomes would be found in the karyotype of a down syndrome female?
a) 45
b) 47
c) 44
d) 46

Explanation:

Step1: Recall normal chromosome number

Normal humans have 46 chromosomes (23 pairs).

Step2: Understand Down - syndrome cause

Down - syndrome is caused by an extra copy of chromosome 21 (trisomy 21). So the total number of chromosomes is 46+1 = 47.

Answer:

B. 47