Mammalian Sex Determination


Sex determination is the process by which genes direct male and female embryos to become distinguishable from each other.

Keywords: Y chromosome; SRY; X‐ovarian maintenance; autosomes; antimüllerian hormone

Figure 1.

Schematic diagram illustrating embryonic differentiation in the normal male. The role of certain genes in formation of the urogenital ridge and indifferent gonad have been deduced in rodents but not necessarily confirmed in humans. Known human genes are designated by standard nomenclature.

Figure 2.

Schematic diagram of the X chromosome showing ovarian function as a function of nonmosaic terminal deletion based on pooled data in familial aggregates; all affected cases are included because their phenotypes are not always concordant. In some cases, patients are described as having premature ovarian failure, but no information is provided on fertility; in the absence of explicit information, it is assumed no pregnancy has occurred. In some younger patients (e.g. >14 year but 20–25 years), there has been little opportunity to demonstrate pregnancy, nor is there assurance that regular menses will continue. Nonetheless, they are designated as having regular menses/fertility2. (Simpson JL and Rajkovic A (1999) Ovarian differentiation and gonadal failure. American Journal of Medical Genetics89: 186–200). (Reproduced with permission of John Wiley & Sons, Inc. © 1999.)

Figure 3.

Pivotal adrenal and gonadal biosynthetic pathways. Letters designate enzymes or activities required for the appropriate conversions. A, 20α‐hydroxylase and 20,22‐desmolase; B, 3β‐ol‐dehydrogenase; C, 17α‐hydroxylase; D, 17,20‐desmolase; E, 17‐ketosteroid reductase; F, 21‐hydroxylase and G, 11β‐hydroxylase; H, aromatase. In addition to these enzymes, Steroid Acute Regulatory protein (StAR), designated A, is responsible for transporting cholesterol to the site of steroid biosynthesis. 17α‐hydroxylase (C) and 17,20‐desmolase (D) activities are actually governed by a single gene. Reproduced with permission from Simpson JL and Elias S (2003) Genetics in Obstetrics and Gynecology, 3rd edn. WB Saunders, Philadelphia. Copyright © 2003 Elsevier.



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Simpson, Joe Leigh(Mar 2008) Mammalian Sex Determination. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0001886.pub2]