I denne undersøgelse blev det undersøgt, hvordan kønsdifferentiering i mennesker fungerer. Det starter med et gen på Y-kromosomet, som får celler i det tidlige embryo til at udvikle sig til testikler. Disse testikler producerer hormoner, der hjælper med at danne mandlige kendetegn, som for eksempel væksten af prostata og penis. Hvis der ikke er dette gen eller hormon, udvikler kroppen sig til kvindelige karakteristika i stedet.
Titel på undersøgelse:
Sexual Differentiation.
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Hele abstrakt på originalsprog:
Sexual differentiation in humans is genetically and hormonally controlled. In response to a signal from a dominant-acting gene on the Y chromosome, primordial cells in the embryonic gonad ridge differentiate into Sertoli cells and affect newly migrated germ cells to differentiate as spermatogonia, thus creating a testis. The cells of the embryonic testis secrete hormones that lead to the development of most, if not all, male secondary sexual characteristics. The Sertoli cells secrete müllerian inhibitory factor (MIF), causing regression of the müllerian ducts and of stray oogonia. The Leydig cells secrete testosterone, causing differentiation and growth of the wolffian duct structures. Dihydrotestosterone, created by metabolism of testosterone, causes growth of the prostate and phallus and fusion of the labioscrotal folds. In the absence of SRY, Sertoli cell differentiation does not occur. Rather germ cells migrating into the primordial gonad differentiate as oogonia and cause interstitial cells to differentiate as granulosa cells. In the absence of MIF and testosterone, the müllerian ducts differentiate and grow as female internal genitalia and the external genitalia are feminized. Several genes have been identified that control testis determination. These include SRY, WT1, SOX9, SF1, XH2, and DAX1. Most of these genes were discovered by analysis of rare cases of sex reversal (genetic sex of one type, gonadal sex of the other type).