L33-Vandenbergh-2003 - Prenatal Hormone Exposure and Sexual...

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Prenatal Hormone Exposure and Sexual Variation Hormone exposure in the womb is instrumental in shaping the sexual anatomy, physiology and behavior of mammals John G. Vandenbergh H ow is an individual's sex deter- mined? In high school biology class you probably learned a basic rule for manimals: Individuals with one X and one Y chromosome develop into males. Those with two X's develop into females. Distinguishing between the re- sulting males and females should be straightforward. Unfortunately for those who like simple rules, the story is far more complex. X and Y chromosomes are only the beginning of sex determination. Biol- ogists have recently taken a closer look at the events between fertiliza- tion and sexual maturity that estab- lish an individual's sexual character- istics. These events help explain variability among individuals in sex- ual anatomy, physiology and behav- ior. For example, an XX individual can exhibit some masculine traits if hormone production or sensitivity is abnormal during early development. In fact, there is almost a continuum of sexual traits between male and fe- male. The ability of environmental in- fluences during development to pro- duce such a continuum demonstrates that another classical dichotomy, be- tween nature and nurture, is in fact a synergy: Genes and environment work together to produce an organism. Spe- cific genes are only tiirned on when the environment of the cell, tissue, organ or organism calls for them. In the case joh)! G. Vmidcnbcrgh is a professor of zoology at North Carolina State Universih/. He received hi? Ph.D. in 1962 fivm Penii State. His current re- search focuses on the effects of prenatal hormone exposure and endocrine disruption on variations in rodent anatomy, physiology and behavior. He has advised the EPA on issues relating to environ- mental endocrine disriiptors. Address: Depart- ment of Zoology, N.C. State University, Raleigii, NC 27695-7627. Internet: vandenbergh@ncsu.edu of sexual characteristics, one mecha- nism by which environmental vari- ables exert their influence is through the activity of hormones. Hormones are substances released by cells into the bloodstream, where they travel throughout the body and influence the function of other, distant cells. Hormone molecules themselves, or the enzymes that produce those molecules, are encoded by the genome, but hormone concentrations can be modulated by a wide array of environ- mental factors, including stress, food consumption, temperature, and time of year. In turn, hormone concentrations modulate the expression of genes in a variety of different cell and tissue types, producing anatomical, physio- logical and behavioral differences. My own studies
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L33-Vandenbergh-2003 - Prenatal Hormone Exposure and Sexual...

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