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. Author manuscript; available in PMC: 2013 Jun 24.
Published in final edited form as: Nat Rev Genet. 2009 Jan;10(1):19–31. doi: 10.1038/nrg2487

Figure 5. Retrogenes, MSCI, and the emergence of mammalian sex chromosomes.

Figure 5

(A, upper part) Illustration of the retroposition of an X-linked parental gene to an autosome. (A, lower part) Illustration of the expression of X-linked parental genes and their autosomal retrogene copies before (in spermatogonial cells), during (spermatocytes), and after (spermatids) the process of meiotic sex chromosome inactivation (MSCI). (B) The evolutionary onset for the selectively driven out of X retroduplication process and MSCI, as well as the inferred origin of therian (eutherians/placental mammals and metatherians/marsupials) sex chromosomes. See main text for further explanations.