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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
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
“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.
- Spring '14