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Unknown General c51237c0

All are true about Lyon's hypothesis except?

A
Only one of X chromosomes is genetically active
B
Only X chromosome from the mother undergoes pyknosis
C
Inactivation occurs on 16th day of embryonic life
D
Gene Xist causes gene silencing
High-Yield Explanation
Ans. (b) Only X chromosome from the mother undergoes pyknosisRef: Robbin's pathology 9th ed. /164Lyon hypothesis is:* Only one of the X chromosome is genetically active* Other X chromosome which can be of paternal or maternal origin undergoes pyknosis and is rendered inactive.* Inactivation of either paternal or maternal X chromosomes occurs at random among the cells of blastocyst by about 16th day of embryonic life* Inactivation of X is because of a gene called Xist which is causing gene silencing DNA methylation.

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