The notes below were taken from a National Geographic television programme called “In the Womb”. I took notes only as it pertained to the subject of the possible genetic causes of sexual preference. I, as a mother of a transexual male to female daughter, found this programme particulary interesting. This research should silence those who believe there is a “cure” for homosexuality or for transexuality. I say “should” silence rather than “will” silence because especially here in South Africa where lesbians are raped by men who believe they will cure these women by raping them, there is no amount of research or education that will ever silence them.
I post this now because I am so proud of my daughter “S” and in the hopes that other parents will find some understanding of their transexual child. The following is directly quoting the programme:
EPIGENETICS
Epigenetics is a new biological field.
Identical twins always have the same DNA code but the functioning of this code may be different. The human genome contains +/- 25000 genes. Scientists are studying a new field called Epigenetics, investigating the epigenome where a series of chemicals which act as switches are capable of activating or deactivating individual genes. One of these switches works by a process called DNA methylation. This causes enzymes within a cell to attach a miniscule molecular compound (a methyl group) to a gene. This chemical can at times activate or deactivate a gene, but the gene remains. In other words the genes DNA profile remains unaltered.
Some unidentifiable factor in early cell development causes a methyl group to attach itself to a gene. The gene is still there but it may have been switched off. The activation and deactivation of genes during early development could explain many of the mysteries that affect us all.
Epigenetics may play a significant role in determining sexual preference. As yet sexual preference is associated with a yet unidentified gene. It may be that epigenetic suppression or activation of this gene could dictate sexual preference. In identical twins, one heterosexual, one gay, epigenetics may be the answer. One twin absorbs more testosterone than the other, making him straight while the other is gay.
It is becoming clear that most aspects of our character and characteristics are not just a product of our genes or our environment. Nature and nurture are inextricably bound, with epigenetics being the tangible, biological link between the two. These subtle changes in the genes expression can be passed down through the generations without affecting the underlying DNA. We are not simply a product of our genes.
In the general population there is less than a 5% chance you will be gay. In twins, however, that statistic changes. If you have a fraternal twin who is gay, you will have a 25% chance that you will also be gay. In identical twins you have +/- a 50% chance of also being gay if your twin is gay, proving that there must be some genetic component to our sexuality. It cannot, however, be all down to genetics or else all identical twins would be either straight or gay. Some other factor must be at play.
In the first few weeks of development all foetuses develop along similar lines and if nothing changed all would be born female. At about the 6th week of development, foetuses with the Y chromosome (male) will form testes and at around the 8th week will release testosterone. This may affect early brain development. This hormone masculinises the body and the brain including a part called the hypothalamus. The hypothalamus is part of the network which defines who we find sexually attractive. Some scientists believe the more the hypothalamus is exposed to testosterone, the more it sets the stage for sexual inclination towards women. Occasionally a male foetus may not produce sufficient testosterone or its brain not absorb sufficient testosterone to shape it along heterosexual lines.
If this theory is correct then it may explain why a male foetus may absorb sufficient testosterone to masculinise its body, but not enough to fully differentiate its brain, causing him to be gay.