sex-chromosome dosage compensation

Definition

Target type: biologicalprocess

Compensating for the variation in the unpaired sex chromosome:autosome chromosome ratios between sexes by activation or inactivation of genes on one or both of the sex chromosomes. [GOC:ems, PMID:11498577, PMID:30049999, PMID:35306885]

Sex-chromosome dosage compensation is a crucial biological process that ensures equal expression of genes located on sex chromosomes, despite the presence of different numbers of these chromosomes in males and females. In most mammals, including humans, females have two X chromosomes (XX) while males have one X and one Y chromosome (XY). This difference in chromosome number could lead to an imbalance in gene expression, as females would have twice the dosage of X-linked genes compared to males. To counteract this imbalance, a mechanism known as X-chromosome inactivation (XCI) occurs in female mammals. XCI involves the silencing of one of the two X chromosomes in each cell of a female during early embryonic development. This inactivation is random, meaning that either the maternal or paternal X chromosome can be silenced. The inactive X chromosome is condensed into a dense structure called a Barr body, which is visible under a microscope. This process ensures that the level of X-linked gene expression in females is equal to that in males. The mechanism of XCI is complex and involves several steps, including: 1. Counting the number of X chromosomes: Cells have a mechanism to count the number of X chromosomes present. 2. Initiation of inactivation: Once the cell detects more than one X chromosome, a process called initiation is triggered. This involves the recruitment of specific proteins and non-coding RNAs to the X chromosome that will be inactivated. 3. Spreading of inactivation: The inactivation signal spreads along the length of the X chromosome, silencing gene expression. 4. Maintenance of inactivation: The inactive state of the X chromosome is maintained throughout the lifetime of the cell. XCI is a remarkable example of epigenetic regulation, where changes in gene expression occur without altering the underlying DNA sequence. It is essential for normal development and function in females, ensuring that they have the correct dosage of X-linked genes. Failures in XCI can lead to various genetic disorders, highlighting the importance of this intricate process.'
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Proteins (1)

Compounds (1)