The SRY gene.
The Embryo - Introduction
The Germ Cells
Germ Line and Somatic Mutations
Conception and Development.
The SRY Gene.
Genetic Errors of Metabolism.
The Fetal Environment.
New Babies Whose Sex is Unknown
Since it was found in the skin of male transsexuals, as in women, it was also thought be a basis for gender identity problems. However this hypothesis has also proved to be unfounded.
The hypothetical agent which produced maleness, which everyone one was looking for, was given the name testes determining factor - tdf
It was a sort of umbrella term for the gene or genes, and the relevant proteins. The final step came from studying XX men, people with female chromosomes who had grown up as men. The first intimation they had that they were not men was when they found they were sterile.
As techniques of genetic investigation improved, it became possible to study the genes of XX men, and show that a tiny part of their fathers' Y chromosome had become attached to the X chromosome that passed to them.
A gene by the name of ZFY looked a likely candidate, until three XX men without ZFY turned up. By this time, the length of genetic material that researchers were looking at was so small they began to doubt that there could be gene there at all.
The search, described in Cookson's The Gene Hunters, (1) ended in a region of only 250 base pairs, which was christened the SRY gene. It probably has a long evolutionary history, being almost identical to a gene involved in reproduction in yeast. When one considers an average gene length is many thousands of base pairs, it seems incredible that something so small could have such a profound effect on world history. If nothing else it is responsible for deforestation of large parts of the world to provide the paper for feminist literature and voyeuristic articles by Fleet Street about transvestites and transsexuals.
It seems that the protein produced by the SRY gene binds to the DNA molecule in specific places, and causes it to bend sharply. It is believed that this change in the three dimensional geometric structure alters the action of a range of other genes. For instance, there are many factors affecting rate of growth, both genetic and environmental, but it is believed that it accounts for the average larger size of men compared to women.
Sometimes the SRY gene is missing from the Y chromosome, or doesn't activate. The fetus grows, is born, and lives as a little girl, and later as a woman, but her chromosomes are XY. Such people are, usually, clearly women to themselves and everyone else. The first premonition that something is wrong may be when menstruation doesn't begin. Occasionally, during meiosis a piece of a Y chromosome transfers to the X, and is carried on into the sperm. Thus the female embryo that results is XX, but develops as a male.
There is a horror story of just such an XY woman,(2) who only discovered the truth after hospital treatment after a diving accident. She then was made to live her next twenty years in abject shame. Her father rushed her into marriage, and her husband told her openly that he had married her because she was a freak. These, of all people should be able to claim that they were 'born that way' and they are an object lesson for those hoping to find respectability in a 'gay' gene.
Bibliography and Good Reading.
Bland, J., (1998) About Gender: The SRY Gene
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Web page copyright 1998-2006
Derby TV/TS Group. Text copyright Jed Bland.
Last amended 08.04.98