Define the Lyon hypothesis

Name: Problem 18, Chapter 5: Essentials of Genetics
Uploaded: 2022-04-13T01:05:18-08:00
Duration: 24 s
Channel: Jennifer Stoner
Description: Define the Lyon hypothesis

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Key Concepts

Dosage Compensation

Dosage compensation is a genetic mechanism used to balance the expression of X-linked genes between the sexes. By inactivating one X chromosome in females, organisms prevent the potentially harmful effects of having a double dose of X-linked gene products.

X-chromosome Inactivation

This is a process in which one of the two X chromosomes in female mammals is transcriptionally silenced early in embryonic development. This silencing ensures that females, like males, have one functional copy of the X chromosome in each body cell, which is critical for normal development.

Random Inactivation and Mosaicism

The Lyon hypothesis proposes that the selection of which X chromosome to inactivate in each cell is random. This random inactivation leads to mosaicism, where different cells in the same organism may have different active X chromosomes, contributing to variability in traits expressed by X-linked genes.

Epigenetic Regulation

X-chromosome inactivation is controlled by a series of epigenetic modifications, including DNA methylation and histone modification, which silence gene expression on the inactivated X chromosome without altering the underlying DNA sequence. This regulation is essential for maintaining the inactive state through subsequent cell divisions.

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