What occurs early in embryonic development of female mammals to prevent "double dosing" of proteins from X chromosomes?Multiple choice question.

Early in the embryonic development of female mammals, a process called X-chromosome inactivation (XCI) occurs to prevent "double dosing" of proteins from X chromosomes. Here's a step-by-step explanation:

1. Female mammals have two X chromosomes, one from each parent. If both X chromosomes were active, it would result in a double dose of the proteins they encode.

2. To prevent this, one of the X chromosomes in each cell is randomly inactivated during early embryonic development. This process is called X-chromosome inactivation (XCI).

3. XCI is controlled by the X-inactivation center (XIC), a region on the X chromosome. The XIC produces a long non-coding RNA called XIST (X-inactive specific transcript).

4. XIST coats the X chromosome from which it was produced, effectively silencing most of the genes on that chromosome.

5. As a result, female mammals, like males, have one functional copy of the X chromosome in each body cell. This prevents the "double dosing" of proteins from X chromosomes.

6. Interestingly, the inactivated X chromosome can be seen in the nucleus as a dense region called the Barr body.

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