Question

In females with a 47, XXX karyotype, how many of the X chromosomes are active?

A 1
B 2
C 3
D This is not a viable karyotype
E This varies on a case-by-case basis

Answer 1

Females with a 47, XXX karyotype have two of the X chromosomes inactivated, leaving only one active X chromosome in each cell for normal gene expression.

Step-by-step explanation:

In females with a 47, XXX karyotype, also known as triplo-X, they typically have two of the X chromosomes inactivated, meaning only one X chromosome is active in each cell. The inactive X chromosomes condense into structures known as Barr bodies. This X chromosome inactivation is a mechanism to compensate for the excess genetic dosage and achieve dosage compensation, ensuring that individuals with multiple X chromosomes do not express more genes than necessary.