What are Barr bodies?

Barr bodies are inactivated X chromosomes that are found only in females as a result of X-inactivation, a process that occurs in organisms that have two X chromosomes, such as female mammals. In order to ensure that females do not produce twice the amount of gene products from the X chromosome compared to males, in one of the X chromosomes in each cell of a female, it becomes inactivated and condenses into a structure known as a Barr body. This mechanism balances the gene expression between the sexes.

In females, this inactivation process means that while one X chromosome remains active, the other is silenced. The presence of Barr bodies is typically used to determine the sex of an individual in certain investigations, as males, having only one X chromosome, do not form Barr bodies. This understanding is crucial in genetics and can also have implications in various genetic disorders linked to X chromosomes.