Which type of chromosomes do Barr bodies represent?

Barr bodies represent inactivated X chromosomes. In species with more than one X chromosome, such as females in mammals, one of the X chromosomes in each cell is randomly inactivated during early development. This process is known as X-inactivation, which ensures that females, who have two X chromosomes, do not express twice the amount of X-linked genes compared to males, who have only one X chromosome.

The structure formed by this inactivation is what is identified as a Barr body. As a result, females have one active X chromosome and one inactive, condensed X chromosome that does not participate in gene expression. This is crucial for normal development and function, contributing to dosage compensation between the sexes.

In contrast, other choices like active Y chromosomes, inactive autosomes, or maintenance chromosomes do not relate to the specific phenomenon of Barr bodies. The identification and study of Barr bodies are significant in understanding X-linked disorders, sex determination, and various genetic conditions.