A Barr body is normally found in the nucleus of a female human cell.

Here's why:

* Barr bodies represent an inactive X chromosome. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).

* In females, one of the X chromosomes is randomly inactivated early in development. This inactivation is called X-inactivation or Lyonization.

* The inactive X chromosome condenses into a dense, inactive structure called a Barr body. This ensures that females don't express twice the amount of X-linked genes compared to males.

So, while both males and females have X chromosomes, only females have Barr bodies because they have two X chromosomes and one is inactivated.