Roses Ablaze
Avatar by Ayumeg
- Joined
- Oct 7, 2003
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Interesting little fact I learned the other day. People on both sides point to the twin studies to disprove the other side. Of all the homosexual men in the study with an identical twin who was separated at birth, 55% of those identical twins were also homosexuals. The instance was significantly higher in identical twins than in fraternal twins. People who think homosexuality is purely genetic point to that to support their theory. But people who think homosexuality is purely psychological or environmental point to the fact that it's still not 100%, as you would expect it to be if homosexuality were purely genetic.
But according to what I read, both sides are wrong.
See, there's this thing called penetrance (I've probably spelled that wrong) that dictates how likely it is that a gene will manifest itself. Things like Hunnington's disease have a 100% penetrance, which means that if you have the gene, you're guaranteed to get the disease. Other genes, however, need some kind of trigger to manifest themselves. Type 1 diabetes is one such trait. It only has a 30% penetrance. That means that if one identical twin has Type 1 diabetes, the other twin, who has the exact same genes, only has a 30% chance of getting the same disease. Schizophrenia has a 48% penentrance. Biploar affective disorder has a 60% penetrance. Only 1 in 3000 Americans have multiple sclerosis. If you have a family member with the disease who isn't a twin, your chances of contracting the disease increase only marginally. If you have a fraternal twin with the disease, however, your chances of contracting it raise to 1 in 44. If you have an identical twin with the disease, your chances of getting the disease rise to 1 in 4.
If there is indeed a "gay gene" it would have an estimated penetrance of about 67%. The other 33% of the men who are nonetheless straight because the gene wasn't triggered would then pass the gay gene onto their children. Furthermore, psychologists have been able to predict a child's sexual orientation as young as the age of five. So whatever this trigger is that causes homosexuality would need to occur very early in a child's life, some theorize in the womb.
But according to what I read, both sides are wrong.
See, there's this thing called penetrance (I've probably spelled that wrong) that dictates how likely it is that a gene will manifest itself. Things like Hunnington's disease have a 100% penetrance, which means that if you have the gene, you're guaranteed to get the disease. Other genes, however, need some kind of trigger to manifest themselves. Type 1 diabetes is one such trait. It only has a 30% penetrance. That means that if one identical twin has Type 1 diabetes, the other twin, who has the exact same genes, only has a 30% chance of getting the same disease. Schizophrenia has a 48% penentrance. Biploar affective disorder has a 60% penetrance. Only 1 in 3000 Americans have multiple sclerosis. If you have a family member with the disease who isn't a twin, your chances of contracting the disease increase only marginally. If you have a fraternal twin with the disease, however, your chances of contracting it raise to 1 in 44. If you have an identical twin with the disease, your chances of getting the disease rise to 1 in 4.
If there is indeed a "gay gene" it would have an estimated penetrance of about 67%. The other 33% of the men who are nonetheless straight because the gene wasn't triggered would then pass the gay gene onto their children. Furthermore, psychologists have been able to predict a child's sexual orientation as young as the age of five. So whatever this trigger is that causes homosexuality would need to occur very early in a child's life, some theorize in the womb.
