How do mammals, including humans, solve the 'dosage problem' caused by the presence of an X and Y chromosome in one sex and two X chromosomes in the other sex?

Key Concepts

Dosage Compensation

Dosage compensation is a genetic mechanism that balances the expression of genes on sex chromosomes between males and females. In mammals, this is primarily achieved through X-inactivation, where one of the two X chromosomes in females is randomly inactivated, ensuring that gene dosage is similar to that of males, who have one X and one Y chromosome.

X-Inactivation

X-inactivation is a process that occurs in female mammals where one of the two X chromosomes is randomly silenced during early embryonic development. This results in a mosaic expression of X-linked genes, allowing females to maintain a similar level of gene expression from X-linked genes as males, thus addressing the potential imbalance in gene dosage.

Sex Chromosomes

Sex chromosomes are a pair of chromosomes that determine the sex of an organism. In mammals, females typically have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The presence of different sex chromosomes leads to variations in gene dosage, which is managed through mechanisms like dosage compensation to ensure proper development and function.