Define the Lyon hypothesis.

Verified step by step guidance

1. Understand that the Lyon hypothesis is a concept in genetics related to X chromosome inactivation in female mammals.
2. Recognize that females have two X chromosomes, but to balance gene expression with males (who have one X chromosome), one X chromosome in each cell is inactivated.
3. Know that the Lyon hypothesis states this inactivation occurs randomly in each cell early in embryonic development, leading to a mosaic pattern of gene expression.
4. Note that the inactivated X chromosome condenses into a structure called a Barr body, which is transcriptionally inactive.
5. Summarize that the Lyon hypothesis explains dosage compensation, ensuring that females do not produce twice the amount of X-linked gene products compared to males.

Key Concepts

X-Chromosome Inactivation

X-chromosome inactivation is a process in female mammals where one of the two X chromosomes is randomly silenced to balance gene expression with males, who have only one X chromosome. This ensures dosage compensation between sexes.

Lyon Hypothesis

The Lyon hypothesis proposes that in female mammals, one X chromosome in each cell is randomly inactivated early in embryonic development, leading to mosaic expression of X-linked genes. This explains phenomena like calico cat coat patterns.

Dosage Compensation

Dosage compensation is the mechanism that balances the expression of X-linked genes between males (XY) and females (XX). X-chromosome inactivation is a key form of dosage compensation in mammals.