New information

Posted on June 30, 2009 by Michael

I’ve posted about “new information” in the past, but I recently wrote this for some friends and figured it may as well go up here, too.

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This is from a YouTube video by some dishonest creationists who poorly edited a video to make it look like Richard Dawkins couldn’t answer a question. It doesn’t deserve to be linked.

“[Is there] an example of a genetic mutation or an evolutionary process which can be seen to increase the information in the genome?”

The answer is yes. But I won’t get to the heart of the question right away. It needs explaining.

A definition of “information” is drastically needed here. It’s a term that doesn’t really mean anything in the given context. However, we can ascribe it some definition which is useful. My best proposition is that it can mean DNA itself (nucleic acids), amino acids, or genes. I’ll tackle DNA first.

Our genetic code consists of four ‘letters’, A, C, T, and G (or adenine, cytosine, thymine, and guanine). These four letters are mixed in a huge number of ways in order to form amino acids. It is amino acids which compose our genes. But let’s slow down.

An amino acid is composed of 3 letters. Let’s say we have CGU. That makes arginine. If we replace that final letter with, say, another “C”, we have CGC. As it happens, that still gives us arginine. Different letter combinations can make the same amino acid. When a mutation occurs which does this, it’s called a silent mutation. It’s neutral and natural selection is blind to it.

Now let’s say we change that middle “G” to an “A”.That gives us CAC, or histidine. This is a completely different amino acid. It’s presence in a given gene in place of arginine can have potentially huge consequences. This single letter substitution is called a missense mutation. (It is also called a point mutation because just one letter was changed; the same applies to the arginine example.)

So as should be clear, single letters of DNA can be considered information because they can have profound effects on genes, which in turn affect how proteins are made. However, we have another avenue.

An amino acid can be considered information because it is more directly responsible for the changes to how a protein operates than a simple letter. Personally, I prefer this option the least, but I digress.

Genes are composed of chains of amino acids. Some can be quite short while others range into the hundreds, even thousands. Recall how an amino acid is composed of a series of 3 letters of DNA. That means those letters go back to back to back to back to etc…, each set of 3 making an amino acid. After one triplet, there’s another. And another. Each “another” is an amino acid. (Eventually, a gene can be defined, at least one way, by identifying where the stop codons are – triplets which tell the gene that it is at its end, thus releasing the amino acid chain.)

But if we’re going to call amino acids information, we may as well go a step further and just say genes. And this gets more to the heart of the question. Genes essentially determine what protein will be made (epigenetic or environmental factors are important, but there’s no need for those here). A mutated gene is mutated information, at least in a sense. So how can an evolutionary process be seen to increase the information in a given genome?

It’s actually pretty simple. DNA is far from perfect. It has incredibly high fidelity, meaning it makes few copying errors, but it isn’t perfect. That’s one way we get mutations. Another thing we can get is extra copies of genes. There are a myriad of ways this can occur which I will not discuss here. But it does occur all the time. In one recent text, I read of 12 copies of a gene for seeing green in relation to eyesight.

So what does it mean to have too many copies of a gene? Sometimes it can mean a lot. A lot of the time, though, it doesn’t have to mean too much, such as with the aforementioned case. But what happens to all those extra copies in the next generation, especially if they have no real world (phenotypic) results? They are not subject to the pressures of natural selection. They are free to mutate in whatever way they ‘please’. This gives these genes a huge range to become useful in other ways. In this case, they may affect vision acuity or color sharpness and that may be an advantage.

This is, for all intents and purposes, new information.

A gene gets duplicated. It mutates. It becomes useful, by chance, in some other way. It is subject to the pressures of natural selection. For that reason, it is maintained in the gene pool. Those with this gene have increased the size of the ‘information’ in their genomes.

Filed under: Evolution | Tagged: , , , , , | 3 Comments »

Why do creationists lie?

Posted on February 25, 2009 by Michael

Here’s an old example of lying creationists:

Basically, some creationists lied to get an interview with Dawkins. They later edited together some footage to make it appear like Dawkins couldn’t answer a simple question: “Can you give an example of a genetic mutation or an evolutionary process which can be seen to increase the information in the genome?” After a long pause (which was unrelated to the overdubbed question), the dishonest creationists paste in some footage of Dawkins answering an unrelated question. It’s patently silly.

So what’s the answer? Dawkins explains the situation and answers the question here. But I’m going to simplify the answer.

An example of a genetic mutation or an evolutionary process which can be seen to increase the information is Down’s Syndrome. Here’s a karyotype for the genetic defect. Look at chromosome 21. It should have two copies but it actually has three. Bam. That’s more information. That is precisely the question creationists want answered: how can information increase in the genome? Mutation.

Of course, the way the question is worded is stupid. Evolution is all about increasing (and sometimes decreasing) information. Duplications do this: one gene is copied twice, one copy diverges to participate in some other function, and bam, we not only have more information, but we have more useful, advantageous information. We see this all the time, all the way down to minute differences in snails.

Let me put in another way. DNA is composed of 4 letters: A, C, T, G. These are in triplet form. That means it takes three letters to make an amino acid. For example, GGC is the amino acid glycine (so is GGA and GGG). A change in one of these letters is a mutation. In most instances, a mutation will change an amino acid. Let’s say the first G in GGC is changed to a C. That makes CGC, which codes for arginine. The gene in which this mutation occurred will now have one amino acid replaced. It is possible that it was have the same basic function as the previous amino acid, but often enough it has a different function. It may make a more ideal protein or an entirely new one. This is a change in information. In order for this information to be maintained, natural selection must act on the organism (or gene, depending on your view). That is the evolutionary process which maintains, increases, and decreases information in the genome. It happens every single day.

I should apologize to my non-creationist readers who didn’t need me to be so basic, but these creationists keep asking questions that are answered in the first weeks of every spring and fall in any intro to bio course.

Anyway, here’s a video of Dawkins talking about dishonest creationists.

Filed under: Creationism | Tagged: , , , , , , | 15 Comments »