Final answer:
A Barr body in a mammalian female cell represents the inactivation of one X chromosome through a process known as X inactivation.
Step-by-step explanation:
A Barr body in a mammalian female cell represents the inactivation of one X chromosome. Early in development, one of the X chromosomes in each cell inactivates by condensing into a structure called a Barr body. This process is known as X inactivation and is a way for females to compensate for their double genetic dose of X chromosome. The particular X chromosome that is inactivated in each cell is random, but all cells derived from that cell will have the same inactive X chromosome.