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Unformatted text preview: an arise when a mutation destroys portions of
the SRY. These individuals, also 46,XY, also develop into baby girls.
One example of this sort of change results in complete gonadal dysgenesis. A gene known as “desert hedgehog” lies in the SRY region of
the Y chromosomes. Desert hedgehog is a member of a gene family that
includes sonic hedgehog and Indian hedgehog—all of which play key
roles during early pattern formation in the developing embryo. When
desert hedgehog fails to do its job, 46,XY fetuses develop normal vaginas and uteruses but only streak gonads. At puberty, these people do
not develop female secondary sex characteristics.10 Clearly the genes
within SRY play major roles in the development of male babies.
Interestingly, though, only about 15 percent of 46,XY females
appear to arise from loss of or mutations in the SRY. So SRY is only part
of the story—a necessary but not sufficient piece along the twisted path
On occasion, a man’s X chromosome will find that piece of Y chromosome left behind in the nucleus, then pick it up and stick it in an
empty pocket. That bit of greediness creates an X chromosome carrying
When a sperm with that X chromosome hooks up with an ovum
carrying the usual X chromosome, then the zygote, embryo, fetus, and
child will have a 46,XX karyotype. But it will enter this world as a baby
boy, or almost. Even though everything looks boyish at birth, as adults,
these people are sterile and generally have smaller than normal testes.11
Otherwise, they are pretty much just like 46,XY people.
To zoologists and botanists, true hermaphrodites are animals or plants
that can play the role of either male or female, sometimes even both,
during sexual reproduction. The ones we are most familiar with, like
hermaphroditic trees, can even fertilize their own ova. By those terms,
there is clearly no such thing as a true human hermaphrodite.
Regardless, there is a group of human beings that reproductive biologists call true hermaphrodites. By definition, a true human hermaph- Where Our Sexes Come From 77 rodite must have both ovarian and testicular tissues either in the same
or different gonads.
Because of the inaccuracy of the word hermaphrodite in reference to
human beings, scientists have recently suggested that we refer to these
people as persons with ovotesticular disorders of sexual development.
Because of its historical significance, however, in this chapter I will stick
The most common karyotype among true hermaphrodites is 46,XX
(one of these X chromosomes usually has the SRY it collected from a Y
chromosome) followed by 46,XX/46XY chimeras or mosaics, and only
On the outside, these people may look like males or females or
something in between. Almost all of them, though, are raised as males
because they have enlarged phalluses. Those phalluses—even if they
began as clitorises—grow to nearly penis proportions because of the
testosterone made by testicular tissue, always a part of a “true” hermaphrodite. Vaginas and uteruses are present in the majority of these
people, and usually at least one testis is palpable in the labioscrotal fold
(that is, one testis has descended into what is a mixture of scrotum and
labium). Breast development occurs with most true hermaphrodites at
puberty, as does menstruation because of the ovarian tissue. But very
few true hermaphrodites produce sperm. Ovulation, though, is common, and many true hermaphrodites with 46,XY karyotype are fertile
and have borne children.
For most people the cause of their hermaphroditism never becomes
clear. Several possibilities exist: sex chromosome chimerism and mosaicism are among the leading possibilities. In either of these cases, one of
the gonads could be 46,XX and the other 46,XY; or individual gonads
could contain cells with both karyotypes. Alternatively, if the SRY region
of the Y chromosome was picked up by another sex chromosome or
even a chromosome other than X or Y, SRY could create a similar situation with cells of two different karyotypes appearing in one or both
Regardless, by their position in the middle, true hermaphrodites
reveal to us the full array of the human spectrum lying in between the 78 Between XX and XY unattainable ideals of the perfect male and the perfect female, between
XX and XY. Lisa May Stevens
Location: Idaho, USA
“The nasty, nasty crows are so very cruel to her, just because she is so very different
. . .” —from one of Lisa May’s poems
“Mother was a little strange at best,” says Lisa May Stevens. “When I was
between five and six years old . . . she would call me to her room, strip
me naked, and begin to dress me in my ‘Lisa May’ clothes. If I objected,
she would pull my dress up and spank me.”
At the time, Lisa May’s name was actually Michael. Lisa May was
his grandmother’s name, but at age five, Michael had no idea why his
mother called him that. At first, Michael resisted th...
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This document was uploaded on 02/04/2014.
- Spring '14