As you may have read here before, I like me some science when I’m commuting or doing dishes – the two main times I put on my iPod and listen to podcasts.
Scientific American continues to deliver the best stuff, both in their short 60-Second Science daily series and in the longer Science Talk episodes.
Now you science-phobes stick with me here. The more you know about how
living creatures reproduce the more entrancing the world becomes.
My favorite episode of the ones I’ve been catching up with has a great piece with University of Wisconsin evolutionary biologist Sean Carroll on the role of gene duplication in evolution. Totally cool stuff.
First, some background: all living creatures have molecules of DNA in their cells. DNA carries genetic information which controls the traits of the living creature. To quote Wikipedia, a gene is a hereditary unit consisting of DNA that occupies a spot on a chromosome and determines a characteristic in an organism. Genes are passed from parent to child in sexual species through the combination of genetic material from each parent. This process is called meiosis (pronounced my-oh-sis).
You’ve probably seen a diagram of DNA which looks like a long zipper. What happens in meiosis (in simplistic terms) is that each of the parent zippers gets unzipped and zips back together with the other half of the other zipper, so you get the mother’s and father’s DNA getting hooked together. What happens in this process is genetic recombination and that is an opportunity for change since the parents’ DNA will not be identical. In other words, meiosis and sexual reproduction produce genetic variation.
What that means is that the living creature could have traits or behaviors which are different from its parents and/or from the offspring of other creatures of the same kind.
And what that means is that it might have a better chance of surviving (or at least breeding) in its particular environment. If so, it becomes more likely than those other creatures to pass its genetic material on to its own offspring. Multiply this by hundreds or thousands of generations and you’ve got survival of the "fittest". By "fittest" I mean the most able to survive (or at least breed) in a particular environment. It’s not "best" – there’s no goal or ideal here; it’s just what currently, under these conditions works.
As you can imagine, migration of a creature into a new area can introduce new genetic variation in the population – the gene pool, if you will – of that area.
The last but certainly not least factor in genetic variation is mutation. Again to quote Wikipedia, mutations can be caused by copying errors in the genetic material during cell division [including meiosis!], by exposure to ultraviolet or ionizing radiation, chemical mutagens, or viruses, or can occur deliberately under cellular control during processes such as hypermutation. The resulting changes can be small or large – even as large as complete duplication of a gene – and may or may not have any effect on the creature’s traits or behaviors.
If a mutation makes a creature less successful at surviving and/or breeding, it’s less likely to pass on its genetic material to future generations. If the mutation is beneficial – i.e. improves the chances of survival and/or breeding – the genetic change is more likely to be passed to another generation. Note that a mutation doesn’t need to otherwise benefit the creature to be beneficial to the continuation of that genetic pattern; it’s all about reproduction.
The overwhelming majority of mutations are neutral; they have neither effect and may even be repaired by the cell. In many cases, though, these genetic changes are simply passed on through the generations doing neither harm nor good to the genetic "fitness" of that creature.
Which brings us back to this cool podcast.
when gene duplication was first noticed and realized to be important,
most researchers thought that what it did was give you one copy of the
gene that could continue performing its original important function,
and another copy that natural selection could then experiment with to
find a new function. But in your paper you talk about the fact that it
might be the case that both genes wander off to find new functions.
Rather than my summarizing it, go give it a listen or read the transcript. It’s totally cool and really well explained. Genetics are so neat!
(And if you want to learn more about molecular biology, I recommend Dr. Zach’s Evolution 101 podcast. Pause the playback of the current episode (grrr) and scroll down to episode 108 "Molecular Biology Primer". Good stuff, which, because of when I first listened to it, I now probably irrevocably associate with doing a jigsaw puzzle in the Egyptian House in Penzance, Cornwall.)