Lyonization
Lyonization (pronounced: lie-on-ization) is a biological process named after the British geneticist Mary F. Lyon, who first proposed the theory in 1961.
Etymology
The term "Lyonization" is derived from the name of Mary F. Lyon, who discovered the process. The term is used to describe the random inactivation of one of the two X chromosomes in female mammals.
Definition
Lyonization, also known as X-chromosome inactivation (XCI), is a process by which one of the two copies of the X chromosome present in female mammals is inactivated. The inactive X chromosome is silenced by it being packaged in such a way that it has a transcriptionally inactive structure called heterochromatin. This process happens early in embryonic development at random in mammals, which means that some cells express an X chromosome from the father, and others the X chromosome from the mother.
Related Terms
- Barr body: The inactivated X chromosome in a female cell, visible in the nucleus as a dense, dark-staining spot.
- XIST (gene): A gene on the X chromosome that plays a crucial role in X-chromosome inactivation.
- Epigenetics: The study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself. Lyonization is a form of epigenetic regulation.
- Dosage compensation: The process by which organisms equalize the expression of genes between members of different biological sexes. In mammals, this is achieved by Lyonization.
See Also
External links
- Medical encyclopedia article on Lyonization
- Wikipedia's article - Lyonization
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