Friday, January 06, 2006

Sexual Orientation? Genetic?

Recently, a research paper was published in the journal Cell (volume 121, issue 5, pp. 785-94) in which changing one gene (fruitless) changed the sexual behavior of fruit flies. How was the sexual behavior of the flies changed? They could make the flies homosexual. Yep. One gene, that’s all it took.

A voice in your head is saying, “That happened in fruit flies. We aren’t fruit flies.”  You are right; we are not fruit flies, but that does not preclude our ability to draw some conclusions from the genetic studies in fruit flies to apply them to humans. Perhaps you want a better, less socially controversial example of genetic experiments in fruit flies shedding light on a human condition? Okay, but first, let me tell you why you should even care about genetic manipulation in fruit flies.

Why fruit flies? They only have four chromosomes. The entire genome is known. It’s easy to tell the difference between males and females. (Check out Wikipedia for more.) How genetically similar are they to humans? About 60% of fruit fly genes have recognizable analogues in humans. Fruit flies are used as models for numerous neurological human diseases such as Huntingdon’s and Parkinson’s. Some diabetes research is involving fruit flies.

So, what exactly did these researchers show by mutating the fruitless gene? First, females with one variant courted other females (who were wild type, meaning no intentional changes had been made to their genes) just like a male would court a female. These “lesbian” flies performed all the courtship rituals except actual copulation. Males with a variant gene showed some courtship rituals with other males, but as this behavior is very rare in wild-type males, a different assay was used. Males with the variant gene did elicit a chaining behavior with other males. A lot more was done to draw their conclusions in this paper, but I won’t discuss all as it gets quite technical.

Think of it this way: this gene exerted its influence not at the moment of courting, but at the time of development (you know after the egg and sperm meet) to create a potential for the behavior. That is the definition of “nature” in the whole “nature v. nurture” debate about any behavior.

Does this mean that human sexual orientation has a genetic component? If just based on this data alone, a conclusion couldn’t be made. As much digging as I did, no human fruitless gene has been identified. However, genetic linkage studies have been done in humans that appear to favor a genetic component for sexual orientation. A good review of the genetic linkage data (well a meta-analysis) can be found here. A more recent review of the scientific literature in print supports the nature, not nurture, hypothesis of sexual orientation in humans. (You can go to a library to find the full text of the review cited above. Warning, all of these articles I’m linking to are highly scientific in writing style and not always easy to comprehend for the non-initiated. It would be like me attempting to read a legal document.)

Next time you hear someone (or even yourself) say that a person chose to be a homosexual, remember this post. Think about the fruit flies. You can even be a Cliff Claven from Cheers spouting off about this research. Imagine how intelligent you’ll sound. Okay, maybe not intelligent, but learned.

And, if you follow my thought process on why I chose this poem, good for you.

By Esther Mathews

I can’t be talkin’ of love dear,
I can’t be talkin’ of love.
If there be one thing I can’t talk of
That one thing do be love.

But that’s not sayin’ that I’m not lovin’—
Still water, you know, runs deep,
An’ I do be lovin’ so deep, dear,
I be lovin’ you in my sleep.

But I can’t be talkin’ of love dear,
I can’t be talkin’ of love.
If there be one thing I can’t talk of
That one thing do be love.


Mr. Baatard said...

This is totally off-topic, but I am now desperately curious. What does HP stand for? Will you tell me if I guess?

House plant?
Hanky panky?
Hewlett Packard?
Howard Phillips (Lovecraft)?
Harry Potter?
Hot potato?
Helicobacter Pylori?
High Pressure?
Home Plate?
Hydrogen Peroxide?
Homosexual Panic? (I thought I should insert some tie-in to your post)

Krishna said...

or perhaps,

homophobic !?