HUMAN SEX DETERMINATION

Human sex determination is a fascinating topic, particularly at the le vel of molecular genetics, as it represents an excellent paradigm for mammalian organ development. Recent progress has seen the addition of several new pieces to this developmental jigsaw puzzle. In mammals, th e Y chromosome is male determining, and encodes a gene referred to as TDF (testis-determining factor), which induces the indifferent embryon ic gonad to develop as a testis. Subsequent male sexual differentiatio n is largely a consequence of hormonal secretion from the testis. In t he absence of the Y chromosome, the testis-determining pathway fails t o be initiated, and the embryonic gonad develops as an ovary, resultin g in female development. (C) 1998 Wiley-Liss, Inc.