What is the Difference Between Random and Imprinted X Inactivation?

Random X inactivation and imprinted X inactivation are two distinct mechanisms that result in the inactivation of X chromosomes in female mammals. The main differences between these two processes are:

1. Timing: Random X inactivation occurs around the time of implantation, while imprinted X inactivation occurs earlier in development.
2. Chromosome: Imprinted X inactivation specifically inactivates the paternal X chromosome, while random X inactivation inactivates one of the two X chromosomes (either maternal or paternal) randomly.
3. Stability: Imprinted X inactivation is less stable and less complete than random X inactivation.
4. Mechanism: Both processes involve the expression of X-linked non-protein coding Xist RNA, but they are regulated by different mechanisms. Imprinted X inactivation is regulated by genomic imprinting, while random X inactivation is regulated by a different process.
5. Tissue: Imprinted X inactivation occurs in extraembryonic lineages, such as placental tissue, while random X inactivation occurs in embryonic lineages.

In summary, random and imprinted X inactivation are distinct processes that result in the inactivation of X chromosomes in female mammals. They differ in timing, stability, mechanism, and the specific chromosome that is inactivated.

Comparative Table: Random vs Imprinted X Inactivation

Random and imprinted X inactivation are two forms of X inactivation occurring in female mammals. Both processes lead to transcriptional silencing of one X chromosome. Here is a table summarizing the differences between random and imprinted X inactivation:

In random X inactivation, both maternal and paternal X chromosomes have an equal probability of being inactivated, while in imprinted X inactivation, primarily the paternally derived X chromosome is chosen to be inactivated. Imprinted X inactivation is less complete and/or stable than the random form, and DNA methylation plays a lesser role in its stability and completion.