Youtor
X chromosome Inactivation simplified
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X chromosome inactivation, also known as lyonization, is a process that occurs in female mammals to equalize the gene dosage between males and females. In mammals, including humans, females have two X chromosomes (XX) while males have one X and one Y chromosome (XY). To prevent an imbalance in gene expression between the sexes, one of the X chromosomes in female cells is inactivated early in development. Here are three key aspects of X chromosome inactivation: • 1. Random Inactivation: X chromosome inactivation occurs early in embryonic development, typically around the time of implantation in humans. It is a random process in which either the maternal or paternal X chromosome is randomly chosen for inactivation in each cell. Once the decision is made, the same X chromosome remains inactivated in all the progeny of that cell. This random inactivation leads to a mosaic pattern of X chromosome activity, with some cells expressing genes from the maternal X chromosome and others expressing genes from the paternal X chromosome. • 2. X-Inactivation Center and Xist Gene: X chromosome inactivation is orchestrated by a specific region on the X chromosome called the X-inactivation center (Xic). The Xic contains the Xist (X-inactive-specific transcript) gene, which is crucial for the inactivation process. The Xist gene is transcribed into a long noncoding RNA called Xist RNA. The Xist RNA coats the X chromosome from which it is transcribed, leading to a series of molecular events that ultimately result in gene silencing and the formation of a tightly packaged, transcriptionally inactive structure called the Barr body. • 3. Escape from Inactivation and Gene Dose Compensation: While most genes on the inactivated X chromosome are silenced, a subset of genes known as escape genes are not fully silenced and remain active. These escape genes can be expressed from both the active and the inactivated X chromosome. The expression of escape genes helps compensate for the reduced gene dosage resulting from X chromosome inactivation. The mechanism of escape from inactivation is not fully understood and can vary among different genes and tissues. • #sciencefacts #xchromosomes #xinactivation #genetics #xist #calicocat #dosagecompenstation #scienceshorts #homeschoolcurriculum
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