Question

Which of the following karyotypes represents Down's Syndrome?

Options

• 47, +13

• 47, +21

• 45, XO

• 47, +18

Answer 1

Down's Syndrome is caused by trisomy 21, resulting in an extra chromosome 21. The karyotype is written as 47, +21, indicating 47 total chromosomes with an extra chromosome at position 21. This is the most common autosomal aneuploidy with an incidence of 1 in 660-700 live births.