The real story is a lot more complicated the real 59

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Unformatted text preview: ere are many more changes to come. Sexual development is a lifelong journey for us all. And though there are some common signposts along the way, such as puberty and menopause, we shall see how the journey is shrouded in mist, and the path is as varied as human beings themselves. 5 Where Our Sexes Come From: The Rest of the Story That is the story of how we come to be—the routes we follow, the stops we make, and the forests and rivers and valleys we pass along the way. It’s more or less everyone’s story about the road from sperm and ovum to boy- or girlhood. Or so we believe, until we look a little more carefully at the map. There are more than a million ways to get from Chicago to Los Angeles. But the route that has been written and sung about most is Route 66—that fine old stretch of macadam that runs across half a continent. But even those who follow the same highway see different things along the way, take different side trips, break down in different places, drink different coffee, and eat different pies. Some people stop now and then, by choice or by necessity. Some even die inside lonely motels left like droppings alongside the road. And though the ones who make it all the way all end up in Los Angeles, by the time they arrive no two of them are alike. But that’s not the story we generally tell. The story we generally tell is a much simpler version, a condensed tale that speaks only of the wonders along the way and what a great time all of the travelers had as they sped westward. The real story is a lot more complicated, the real 59 60 Between XX and XY ride a great deal more dangerous, the actual experience a good deal more nerve-wracking. The simplest stories are rarely the truest. The same can be said about sex. Most of the tales we spin about human sex determinations leave out the busted axle in Baxter Springs, the blown radiator in Barstow, the week spent washing dishes in Tucumcari for gas money. Most of the tales we tell about sex speak only a little of the road from conception to birth and instead move quickly into the safety of a pink or blue fog. The shame in that is that this is our story, and the complete tale is full of wonders. The Truth about X and Y “OK, how do you know what sex you are, or what sex anyone is, for that matter?” I ask my class. Alicia, a bright young woman majoring in biochemistry, raises her hand. “Yes?” “Chromosomes,” she says. “Men are XY and women are XX.” “But wait a minute,” says Clarisse, a liberal arts major. “What about XXY people? Or XO?” Another student raises his hand and says, “Aren’t there some women who are XY?” And from there the discussion descends into chaos. In spite of the confusion, though, it still seems that sex should have something to do with chromosomes. In fact it does, at least sometimes, but not how most of us imagine it does. Lying like gene-stuffed serpents inside each of our cells, chromosomes seem to have acquired mysterious powers. Inside those coils of DNA, geneticists have told us, is our future—the color of our hair and eyes, the length of our bones, the size of our brains, the paths of our lives, and most directly and importantly, our sexes. But before a chromosome can do anything except sit around and soak up mutations, it needs aid, usually a protein. Proteins open chromosomes up and close Where Our Sexes Come From 61 them down, turn genes on or off, build a cell up or break it down. Every step on the way from zygote to adult is directed by one or more proteins. And each protein has its own set of problems and its own peculiar way of dealing with the world. That’s a little like having a set of blueprints that change in critical ways every time someone opens them up for guidance. And it’s a lot like having carpenters, electricians, plumbers, and contractors who all speak slightly different languages. So, even if the blueprints were perfect to begin with (which they never are), the project’s possible outcomes are as variable as the people who use those blueprints, as convoluted as spoken languages, as uncertain as a lottery. It’s the same with sex, but even more so. Sex Chromosomes Lost and Found Contrary to what biology texts have alleged as law, some people—genuine human being people—don’t have forty-six chromosomes. People with Down syndrome, for example, have forty-seven chromosomes, including an extra copy of chromosome twenty-one. That extra chromosome leaves its mark on these people—epicanthic folds in their eyelids, the slant to their eyes, simian creases in their palms, the often-associated mental retardation, their unabashed beauty. There is a moment in most every cell’s life when it imagines that it contains enough of everything for two. As that idea blossoms, the cell gathers together all of its chromosomes, waiting for the universe’s own hand to split them apart and deliver one into each of the new cells. On the road to sperm or egg, in the final division of meiosis, the chromoso...
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This document was uploaded on 02/04/2014.

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