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How Do You Know Whether You Are Male Or Female?
New research published online this week in the open-access journal PLoS
Biology investigates this basic and much-studied question in the fruit
fly,
and comes to a surprising new conclusion.
In mammals, male or female development depends on the presence of the Y
chromosome, which is only found in males because it includes masculinizing
genes. But other animal groups have evolved different systems. James
Erickson and Jerome Quintero at Texas A&M University studied the mechanism
of sex
determination in the fruit fly, Drosophila melanogaster.
Previous studies in the fly suggested that it was the ratio of X
chromosomes (the "female" chromosome, of which there are two copies in a
female
fly, and just one in a male) to the non-sex chromosomes (the autosomes)
that determined the sex of a fly embryo. However, this new paper indicates
that rather than being dependent on the ratio, it is the number of X
chromosomes that is important. Sex is determined during a very specific
and short
stage in embryo development, and only two X chromosomes can produce enough
of a signal to feminize the embryo during this window of opportunity.
Citation: Erickson JW, Quintero JJ (2007) Indirect effects of ploidy
suggest X chromosome dose, not the X:A ratio, signals sex in Drosophila.
PLoS
Biol 5(12): e332. doi:10.1371/journal.pbio.0050332
Please click here
http://www.plosbiology.org
Public Library of Science
185 Berry Street, Suite 3100
San Francisco, CA 94107
USA
Cum de ºtii dacã eºti bãrbat sau femeie? - How Do You Know Whether You Are Male Or Female? - articole medicale engleza - startsanatate