Multiple Choice
Which of the following best describes the function of the Xist gene in X chromosome inactivation?
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3. Extensions to Mendelian Inheritance
X-Inactivation
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Which of the following statements best applies to the inactive X chromosome in mammalian females?
A
It is actively transcribed to compensate for the active X chromosome.
B
It is always the paternal X chromosome that becomes inactive.
C
It is completely degraded during early embryonic development.
D
It is largely transcriptionally silent due to extensive DNA methylation and histone modifications.
Verified step by step guidance1
Understand that in mammalian females, one of the two X chromosomes undergoes a process called X-inactivation to balance gene dosage between males (XY) and females (XX).
Recognize that the inactive X chromosome is not actively transcribed; instead, it becomes largely transcriptionally silent to prevent overexpression of X-linked genes.
Know that this transcriptional silencing is achieved through epigenetic mechanisms such as extensive DNA methylation and histone modifications, which compact the chromatin and reduce gene expression.
Be aware that X-inactivation is typically random in each cell, meaning either the maternal or paternal X chromosome can be inactivated, rather than always the paternal one.
Note that the inactive X chromosome is not degraded; it remains present in the nucleus as a condensed structure called the Barr body.
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