This can cause otherwise normal 46xx fetuses to

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Unformatted text preview: have if the doctors had not “altered” her at birth. I was lightning-struck! I could see exactly what had been done— cut here and here, stitch there and presto! . . . Pretty much everything in my early life made sense at that point. I understood why everyone did what they did, and I understood their motivation. I was incredibly angry that nobody told me! But at least I understood, and I knew they thought they were doing the best thing for me. Thankfully, I finally defied everyone and did what was right for me before it was too late. For some time now Dianne has been active in intersex and transgender support groups trying to help others who are struggling with the same issues that she wrestles with. “After all, I have been there, done that,” she says. “I may carry the ‘scars’ of years of mistreatment, misdiagnosis, and misunderstanding, but it also taught me a compassion and acceptance beyond the ordinary that I can extend to others.” Normal Chromosomes Wearing Abnormal Genes Like a typewriter with a bad key, sometimes a chromosome taps out a story peppered with mistakes. Every time the writer reaches for an “o,” the typewriter slaps down an “e.” “Looking forward” becomes “leeking ferward.” The sense of it blurs and the story takes an abrupt swing. When a chromosome does that, people change in unpredictable ways. Besides the genes found on X and Y chromosomes, there are several other genes involved in the sexual development of the fetus. We already know of nearly two dozen such genes, and undoubtedly there are more. A detailed consideration of the enzymes involved in sex development— the nature of each of these enzymes and the corresponding genes, as well as the consequences of mutations—is more than this book can handle. But with so many genes involved, the alternative outcomes Where Our Sexes Come From 99 of fetal sexual development are like the birds of the air—varied and wondrous. But, also like birds, some are so especially wondrous they deserve a little more attention. Congenital Adrenal Hyperplasia Within the urogenital ridge—what will become the external and internal genitalia of the fetus—the gonads and related sexual tissues develop close to the kidneys and the adrenal glands. The adrenal glands, like the gonads, produce hormones critical to determining the sex of the developing child. These hormones include cortisol and the adrenal androgens, especially androstenedione, a precursor to testosterone. When the adrenal glands overdevelop—a condition called congenital adrenal hyperplasia—they can produce enormous quantities of cortisol and adrenal androgens. This can cause otherwise normal 46,XX fetuses to develop clitorises that to varying degrees more closely resemble penises and scrotums—female pseudohermaphrodites. Mutations in at least five different genes can cause congenital adrenal hyperplasia. And changes in each of these genes cause a distinct set of chemical and physical changes in the child. Baby girls begin to look like baby boys. One of these genes is responsible for an enzyme called 21-hydroxylase. Mutations in this gene result in masculinization of the external genitalia during fetal development. Interestingly, mutations in the gene for 21-hydroxylase are some of the most common mutations seen in infants. In some populations, such as the Ashkenazi Jews, as many as one in three babies have abnormal 21-hydroxylase genes, as do one in seven people in New York City and one in sixty people in the general population.13 The symptoms vary considerably from person to person, but genetic heritage clearly plays a role. Changes in the fetus range from simple clitoral hypertrophy (a large clitoris that may more closely resemble a penis) with normal ovaries, vagina, and uterus, to retention of the urogenital sinus, which is the space where the urethra and vagina usually come together to form a single opening to the exterior of the body. On the other hand, some 100 Between XX and XY 46,XY fetuses with congenital adrenal hyperplasia develop like 46,XY fetuses without adrenal problems, and the external genitalia of these infants look like those of a traditional male at birth. Intersex as a Way of Life Among Other Animals For those who imagine males and females as opposite sexes, hyenas are a conundrum. In fact, the appearance and biology of spotted hyenas have been enough to force some of us to rethink just what we mean by male and female. Nearly two thousand years ago, Ovid and Pliny the Elder both reported that they noticed something truly extraordinary about spotted hyenas: they all appeared to be males. Spotted hyenas are common in the savannahs and woodlands of sub-Saharan Africa. Apparently Pliny, as had Ovid before him, booked transit from Rome to explore the Dark Continent. What each found when he first looked upon packs of the animals was that every spotted hyena appeared to have a penis and a scrotum. That led Pliny the Elder to propose that hyenas could chang...
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This document was uploaded on 02/04/2014.

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