Having extra copies of certain genes helps fish live in AntarcticaI’ve always loved weird creatures. Bacteria that can live in boiling mudpots. Weird tubeworms huddled around deep sea hydrothermal vents. Fish that live in below freezing water.

What I like is learning how these beasts have adapted to their incredibly harsh environment. More specifically, what changes have happened in their DNA that allow them to live where no other animal could.

In this blog I’ll focus on those poor fish living in the waters off Antarctica. These waters are icy cold and the fish aren’t warm blooded. Which means their body temperature is the same as the water around them.

Most biological processes do terribly under these conditions. Proteins don’t fold right, enzymes work incredibly slowly, fats glob up. It is astonishing that these fish survive at all.

Scientists figured out back in the 70’s that these fish evolved a special antifreeze protein to keep their blood from freezing. Since then they’ve done other experiments that show other adaptations to the cold too.

In a new study, scientists from the University of Illinois and the Chinese Academy of Sciences decided to take a look at as many genes and as much of the DNA of these fish as they could. What they found was that lots of genes are turned up in these fish compared to relatives that live in warmer waters. And that many of these genes are turned on higher because the Antarctic fish have extra copies of them.

The genes they found that were different made sense. For example, there are a bunch of genes that make proteins called chaperones. Chaperones help other proteins fold up right. In this cold, proteins need all the help they can get!

Also they found that there were more of the proteins that scavenge reactive oxygen species (ROS) in these fish. This makes sense because colder water has more oxygen.

O2 is a pretty nasty molecule that tends to create even nastier chemicals (ROS) that beat up on DNA and proteins. We all have proteins whose job it is to defuse these chemicals. These fish make more of these proteins.

A few years ago it would have been surprising to find that the way these genes made more proteins was by duplicating themselves. Not anymore.

As we look closely at the DNA of various creatures, we are finding that gene duplications (and deletions) happen a lot. Even in people.

For example, people from cultures that eat a lot of starch have extra amylase genes. (This gene makes amylase, a protein that helps breakdown starch.) Some people are resistant to HIV (the virus that causes AIDS) because they have extra copies of the CCL3L1 gene. And so on.

Our DNA is much less stable than we thought. Which is one way we can better adapt to our surroundings. I can’t wait to see what they learn about those tubeworms!

Bobby is more likely to be gay than Greg.

Last blog I talked about some studies that link homosexuality and genes. The most powerful studies are those that compare identical twins to fraternal twins. These studies show that both twins in an identical pair are more likely to be gay than are both twins in a fraternal pair. Since identical twins have the same DNA, this suggests that something genetic is going on.

But no study showed that if one identical twin was gay, then the other one was always gay as well. We’d expect both twins in an identical twin pair to share a purely genetic trait 100% of the time. Because they don’t, the environment definitely plays a role. But not like you might think.

By environment I don’t mean certain family situations (although these sorts of factors probably contribute as well). What I am referring to are environmental factors that can affect brain development. Factors like viruses, hormones, or maybe even antibodies.

We know, for example, that the more older brothers a man has, the more likely he is to be gay. Even if he doesn’t live with the older brothers.

This suggests that something biological is going on. It is as if the mother’s body remembers how many sons she has had. One way this might happen is through her immune system.

Perhaps when a mother has a son, she makes antibodies to something having to do with carrying a male child. The more sons she has, the more antibodies she makes. At some point, she makes enough antibodies to affect brain development and the younger son is now gay.

Of course, not every youngest son is gay– he is just more likely to be homosexual. Other factors have been reported to increase the chances that someone is gay too. These include being left handed, having a counter-clockwise hair whorl and maybe even different finger lengths. All of these traits are associated with differences in brain development.

There are apparently many paths to a homosexual brain. This isn’t surprising as human sexuality is much too complex to be due to a single gene or environmental factor. Most likely, it is the result of many factors all working together.

Some gay men may have inherited genes that made environmental factors more likely to affect their sexuality. And some gay men may have been exposed to multiple environmental effects that affected their sexuality despite their genes.

I think you can appreciate how these kinds of complex interactions can make finding “gay” genes incredibly complicated. And why it is hard to pinpoint the environmental effects that contribute to becoming homosexual as well.

Dr. Barry Starr is a Geneticist-in-Residence at The Tech Museum of Innovation in San Jose, CA.

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