The Barr body is an example of tightly compacted inactive chromatin found in mammalian females.

The Barr body is an example of tightly compacted inactive chromatin found in mammalian females.

• A. Barr body
• B. Nucleolus
• C. Centromere
• D. Nucleosome

Answer: (A)

In mammals, female cells balance gene expression by inactivating one of the two X chromosomes, a process that makes that chromosome become highly condensed heterochromatin. This condensed X, which appears as a dense, inactive body in the nucleus, is known as the Barr body. It represents the transcriptionally silent form of the X chromosome and is typically visible in female somatic cells (males usually don’t have a Barr body because they have only one X). So the statement is describing the Barr body correctly: it is tightly packed, inactive chromatin specific to the extra X chromosome in female cells. The other options refer to different cellular structures: the nucleolus is the site of ribosomal RNA production, the centromere is the chromosomal region essential for separation during division, and the nucleosome is the basic unit of DNA packaging within chromatin. The Barr body is not any of these; it is the inactivated X chromosome itself.

In mammals, female cells balance gene expression by inactivating one of the two X chromosomes, a process that makes that chromosome become highly condensed heterochromatin. This condensed X, which appears as a dense, inactive body in the nucleus, is known as the Barr body. It represents the transcriptionally silent form of the X chromosome and is typically visible in female somatic cells (males usually don’t have a Barr body because they have only one X).

So the statement is describing the Barr body correctly: it is tightly packed, inactive chromatin specific to the extra X chromosome in female cells. The other options refer to different cellular structures: the nucleolus is the site of ribosomal RNA production, the centromere is the chromosomal region essential for separation during division, and the nucleosome is the basic unit of DNA packaging within chromatin. The Barr body is not any of these; it is the inactivated X chromosome itself.