On Sun, 17 Sep 2000, Linda Walsh wrote:
> Browsing the sex chapters of assorted biopsych texts, preparing for class
> tomorrow, I came across a discrepancy I thought Tipsters might be able to
> resolve. Rosenzweig et al states that Turner's syndrome is associated with
> poorly developed but recognizable ovaries. Klein says that female development
> proceeds up to a point, but that 2 X chromosomes are necessary for the ovaries
> to produce eggs, so Turner's results in infertility. Carlson, on the other
> hand, says that 2 X chromosomes are necessary to produce ovaries, thus
> individuals with Turner's have no gonads at all. This sounds wrong to me. Is
> there anthere total absence of ovarian function in Turner's (e.g. secondary sex
> chars, menstruation). Anyone know the specifics of why 2 X are necessary for
> ova production?
I'm now discussing non-disjunction in my child psychology
lectures, so I thought I'd see what I could find related to this
question. I'd say they're all about right. I have an
authoritative source (White, 1994) which states:
"The classical features [of Turner] include...failure of gonadal
development [this and following references omitted]. Germ cells
are present in the gonads of 45,X embryos, but begin to
deteriorate in late fetal life. By early childhood, there are
usually no oocytes remaining, and the gonads consist of fibrous
streaks...In the Turner syndrome, it has been proposed that
absence or structural abnormality of one X chromosome precludes
or disrupts the normal X pairing process in the fetal ovary,
which eventually leads to premature germ cell loss."
But my real motivation in responding is so I can tell you about a
truly remarkable new hypothesis to explain why boys are much
more antsy than girls. Turner syndrome is the clue (see
McGuffin & Scourfield, 1997)
Turner cases have only a single X, which they get either from the
father or the mother (about 80% from the mother, meaning that the
sperm is defective in these cases). Amazingly, when they get the
X from the mother, they turn out to have social difficulties,
such as "offensive or disruptive behavior" much more frequently
than when they get the X from the father. This is the phenomenon
of genetic imprinting: who passes the chromosome on counts.
And here's the great hypothesis. Boys have a Y, supplied by their
father, and one X chromosome, which they must get from their
mother. The same X that makes Turner girls misbehave. So it's
possible that it's the mother's X which makes the boys act like
boys. Ironic, isn't it?
-Stephen
McGuffin, P., & Scourfield, J. (1997). A father's imprint on his
daughter's thinking. Nature, 387, 652--
White, B. (1994). Ch. 9. The Turner syndrome: Origin, cytogenetic
variants, and factors influencing the phenotype. In:
Broman, S. and Grafman, J. (eds) Atypical Cognitive
Deficits in Developmental Disorders. Lawrence Erlbaum.
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Stephen Black, Ph.D. tel: (819) 822-9600 ext 2470
Department of Psychology fax: (819) 822-9661
Bishop's University e-mail: [EMAIL PROTECTED]
Lennoxville, QC
J1M 1Z7
Canada Department web page at http://www.ubishops.ca/ccc/div/soc/psy
Check out TIPS listserv for teachers of psychology at:
http://www.frostburg.edu/dept/psyc/southerly/tips/
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