Question

How many total chromosomes does a human with Down's Syndrome have?

Options

• 47

• 46

• 48

• 45

Answer 1

A human with Down's Syndrome has 47 total chromosomes (44 autosomes + 2 sex chromosomes + 1 extra chromosome 21). This is represented by the karyotype 47, +21. The extra chromosome 21 results from nondisjunction errors during meiosis, typically during maternal oogenesis.