Which of the following best describes the function of the XIST gene in X chromosome inactivation?

• A. The XIST gene codes for an enzyme that methylates DNA on the X chromosome being inactivated.
• B. The XIST gene on the X chromosome that will remain active is expressed to produce multiple RNA molecules that bind to the X chromosome to be inactivated and effectively cover it up, thereby generating a Barr body.
• C. Together with other proteins, the protein product of the XIST gene binds to histones and induces supercoiling of the DNA in one of the X chromosomes, thus inactivating it.
• D. The first and second listed responses are correct.
• E. The XIST gene on the X chromosome that will be inactivated is expressed to produce multiple RNA transcripts that bind to that chromosome and effectively cover it up, thereby generating a Barr body.

Answer: (E)

Verified step by step guidance

1. Understand the context: X chromosome inactivation is a process by which one of the two X chromosomes in female mammals is inactivated to ensure dosage compensation between males and females.
2. Identify the role of the XIST gene: The XIST gene is crucial in the inactivation process. It is located on the X chromosome that will be inactivated.
3. Recognize the mechanism: The XIST gene is transcribed into RNA, not a protein. These RNA molecules coat the X chromosome from which they are transcribed.
4. Understand the outcome: The coating of the X chromosome by XIST RNA leads to its inactivation, forming a structure known as a Barr body.
5. Clarify the correct description: The correct function of the XIST gene is that it produces RNA molecules that bind to the X chromosome to be inactivated, effectively covering it and leading to its inactivation.