Rob Tisinai

A Minnesota state representative opposed to marriage equality recently said, “We’re not talking about an immutable characteristic like the color of your skin. The human genomap was completed in 2003. There is no gay gene.” We’re likely to see this non-fact popping up more and more as the Supreme Court hearing nears, so I’m reprinting this piece I posted two and a half years ago.

Not long ago I saw this on NOM’s Facebook page:

They’ve mapped the human genome. There’s no gay gene!

I can’t find the quote anymore, but that doesn’t matter because this mistake is all over the Internet. The most common source seems to be this deeply flawed statement:

On April 14, 2003, the International Human Genome Consortium announced the successful completion of the Human Genome Project—two years ahead of schedule. The press report read: “The human genome is complete and the Human Genome Project is over” (see “Human Genome Report…,” 2003, emp. added). Most of the major science journals reported on the progress in the field of genetics, but also speculated on how the information would now be used. The one piece of information that never materialized from the Human Genome Project was the identification of the so-called “gay gene.”

So much wrong with this.* But that last sentence is especially bad:

The one piece of information that never materialized from the Human Genome Project was the identification of the so-called “gay gene.”

Actually, no — lots of information didn’t materialize from the project. Like the number of genes. Where they’re located on the genome. What those genes do. The same group that issued the press release also said this:

A sampling follows of some research challenges in genetics–what we still don’t know, even with the full human DNA sequence in hand. Gene number, exact locations, and functions

Gene regulation

DNA sequence organization

Chromosomal structure and organization

And that’s just the beginning.

I can see why people are confused. What do you mean we don’t know how many genes there are? We’ve mapped the whole genome!

But that’s not what mapping the genome means. What does it mean, then? Time to get all dorky:

The human genome is made up of 24 chromosomes 23 pairs of chromosomes.

Chromosomes contain DNA, the genetic instructions governing an organism.

DNA is shaped like two long curly strands (imagine a double slinky) held together by “base pairs” of chemicals called neucleotides.

Wikipedia offers a great description of how these elements fit together:

DNA is made of two strands that pair together like the two sides of a zipper.

The nucleotides are in the center, like the teeth in the zipper, and pair up to hold the two strands together.

Importantly, the four different sorts of nucleotides are different shapes, so in order for the strands to close up properly, an A nucleotide must go opposite a T nucleotide, and a G opposite a C.

This exact pairing is called base pairing.

And what’s a gene? A gene is a stretch of DNA, a sequence of base pairs. Now here’s the key:

To say we’ve mapped the human genome is to say we’ve sequenced all the base pairs.

That’s it. It does not mean we’ve identified all the genes in the sequence. And it sure doesn’t mean we know the function of each gene we have identified.

Here’s a metaphor of my own. Imagine a chromosome is like a cobblestone highway winding through America. We can walk the highway and identify every cobblestone (or nucelotide), but that doesn’t mean we know what state (or gene) we’re in, or even how many states there are — much less what each state does.

You can see this by looking at the genes that researchers have only isolated recently:

The gene that… Was identified in… Lightens skin color 2008 Makes hair curly 2009 Grows tooth enamel 2009 Causes nearsightedness 2010 Makes your earwax wet or dry 2006

All of this, discovered after the Human Genome Project was “complete.”

Unfortunately, anti-gays depend a lot on junk science and ignoring the facts they don’t want to see. The passage I quoted up top is all over the Internet, so it would be handy to condense this rebuttal into a simple statement that doesn’t require carrying around a nucleotide zipper diagram.

This is what I’ve come up with:

Mapping the genome just means they’ve figured out its chemical structure. They still haven’t broken it down into all the individual genes yet. They’re not even sure how many human genes there are. I mean, they didn’t find the gene for near-sightedness until 2010, seven years after the genome project was complete. Who knows what else they’ll find next?

For the record, I have no idea whether there’s a gay gene. Or a gay combination of genes. I wouldn’t be surprised if it’s a lot like height: We know there’s a genetic component, but environmental factors play a part, too, like hormones in the womb, and childhood diet and health. Yet even though it’s not 100% genetic, that doesn’t mean it’s a choice.

Either way, though, this particular anti-gay argument is dripping with irony. By attempting to cloak their homophobia in science, they do nothing but reveal their scientific illiteracy.

But at this point in the game, are you really surprised?

* The authors of this statement seem to be lying. The phrase,”The human genome is complete and the Human Genome Project is over” doesn’t appear anywhere in the press release (the authors direct you to the press release here, though that page merely links to the release itself). I don’t know why they felt the need to lie, because the Project is indeed complete. Maybe they were just sloppy, not dishonest. It’s aggravating, nonetheless.

UPDATE: Here’s a great graphic illustrating the relationship between the genome, chromosomes, DNA, genes, and base pairs.