A man and woman are eager to determine the sex of their unborn child and have asked the nurse at the fertility clinic how this is possible at an early stage of in vitro development. Which of the nurse's responses best captures the genetic rationale for early sex identification through tissue samples?
A) "The inactive X chromosome can be visible in a female."
B) "The cells of a male contain a Barr body that can be visualized."
C) "A normal female lacks Barr bodies."
D) "The number of visible Y chromosomes indicates the sex."

Question

Quizplus · Accepted Answer

The fact that the inactive X chromosome can be visible as a Barr body in a female allows for the extrapolation of the number of X chromosomes and thus the sex associated with the cells. Normal male cells lack Barr bodies, but they are present in females. The number of X chromosomes ultimately determines the sex of an individual.

A Man and Woman Are Eager to Determine the Sex