Monday, January 24, 2011

Genetics will not be used to abort straights OR gays

Not because of ethics, necessarily, but because of science.

Genetics is complicated. This is a concept that all non-scientists, regardless of political leaning, seem to have a hard time grasping. I've heard liberals who are worried that advances in genomics will result in a simple prenatal test, which bigots would gobble up to make sure they're not growing the next Ricky Martin or Ellen DeGeneres. This always seemed like a silly fear, since people from the religious right also tend to be not so fond of abortion.

But it's not just the liberals. Now World Net Daily is worried gays are going to abort straight babies:
If two homosexual men want to use in vitro fertilization to conceive a baby and then use genetics technology to ensure the baby is also "gay," while disposing of any "straight" embryos, would the law have any ethical problems with that? John A. Robertson of the University of Texas Law School is the chair of the Ethics Committee of the American Society for Reproductive Medicine and an advocate of what his book "Children of Choice" calls "procreative liberty." In a paper for the Washington, D.C., think tank Brookings Institution, Robertson presents a futuristic scenario where advancing science and society's evolving morality could create a once only dreamed-of ethical dilemma:

"Larry, a pediatrician, and David, a wills lawyer, meet in their late 20s, fall in love, and marry on June 15, 2025, in Indianapolis," Robertson writes. "By 2030, they are well-enough established in their careers to think about having their own child. Larry's 24-year-old sister Marge has agreed to donate her eggs, and David will provide the sperm, so that each partner will have a genetic connection with the child. … In the process, Larry and David come to realize that they would prefer to have a male child that shares their sexual orientation." He continues, "The clinic doctors are experts in embryo screening and alteration, but cannot guarantee that the resulting embryos will in fact turn out to be homosexual. To increase the certainty, they will insert additional 'gay gene' sequences in the embryos."
Of course gays, what with their agenda and all, are going to engineer some gaybies! So much more reasonable. Heterosexuals are doomed.


I don't think you should chose an embryo based on sexual orientation, but let's put ethics aside for a moment and talk about the science. The ethics debate is irrelevant because the "science" they discuss is ludicrous. As someone who's studying the "mushrooming" field of genomics, let me try to explain.

Homosexuality almost certainly has a genetic component (1) and has potentially been associated with certain areas of the human genome (2). However, "genetic component" does not equal "gene." Genetics is way more complicated than what you learned back in middle school - it's not just single genes with dominant and recessive alleles. You can have multiple genes affecting the same trait, numerous alleles per gene, and interactions between certain combinations of certain alleles between different genes.

If you do find a single mutation that's associated with homosexuality, it's likely to be very very rare in humans. If it was more common, we would have identified it a long time ago using traditional genetic tools. Such a mutation would be able to explain just a small percentage of homosexuality. I'm sure by now you've heard of studies in the news that have claimed to find a genetic component to heart disease, or schizophrenia, or something. If you read the fine print, it usually only explains something like 3% of the disease. Not really predictive enough to start aborting the breeders.

If this sounds complicated already, it's just the tip of the iceberg. You can also have mutations in regulatory regions of genes. These aren't DNA sequences that code for the actual protein, but rather regulate things like how often or in what tissue that protein is made. You can also have copy number variants (CNVs), where some people have extra (or less) copies of a certain gene.

Thanks to massive advances in technology, we can study stuff like mutations, regulatory regions, and CNVs pretty well now... but they're still not the full story. Often times a single "hit" - one mutation in a gene, or one big deletion in a chromosome - isn't enough to actually cause a trait. This is especially true when dealing with neurological traits like autism or learning disabilities, and may be implicated in a behavioral trait like homosexuality. Often times you need multiple mutations or deletions - or a combination of both - until you actually show the trait in question.

But it's still even more complicated than that. It's not as easy as saying Mutation A + Deletion 2 = FABULOUS! Both of these events are extremely rare, and there are likely thousands and thousands of different combinations of "lesions" (messed up DNA) that could cause a trait. So even if you sequenced a baby's full genome, you'd have no idea what all the de novo (new) mutations and deletions would do, because they've likely never been seen in that combination before.

And all of this isn't even taking into account epigenetics (which can further regulate DNA, and can even differ between twins), and environmental factors (which can range from hormones you're exposed to in the womb, to listening to too many show tunes as a small child).

So the odds of Teh Gay being boiled down to a simple test, or a simple gene you can use to infect the population? Basically zero.

Genetics is complicated, and I don't expect everyone to be able to understand it in depth. Even as a first year PhD student, I tried my best to write the above paragraphs jargon free and without unnecessary detail. But at the very least, admit that it's complicated and you have no real idea how it works instead of concocting conspiracy theories.

Though I have to admit, it's amusing that these are the same type of people who claim that simply knowing gays exist, or worse, allowing them to be parents is enough to turn someone gay. Which is it, nature or nurture? Oh right, whatever currently fuels your paranoid hate speech the most.

But you know, maybe the totally wacked out religious types would be content aborting fetuses if they even had a 5% higher chance of being gay. In which case, I'd like to point them to a study that showed each older brother a man has increases his probability of being homosexual by 28% to 48% (3). If they really want to avoid bringing gay men into the world, stop giving birth to sons. And if you're not willing to rely on abortion, only have one child.

A win-win situation, if I do say so myself.

1. Bailey JM and Pillard RC (1991). A genetic study of male sexual orientation. Archives of General Psychiatry, 48:1089-1096.
2. Mustanski BS, et al. (2005) A genomewide scan of male sexual orientation. Human Genetics, 116(4):272-8.
3. Blanchard R (1997) Birth order and sibling sex ratio in homosexual versus heterosexual males and females. Annual Review of Sexual Research, 8:27-67.

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