In evolution, what are the mechanisms by which extra genes can be added to a simple genome?

Question

I understand that nuleotide polymorphism can arise by the mutation of already existing nucleotides, but how do you get from a simple organism with few genes to a complex one with many?

Most of the arguments in favour of ID are pretty easy to counter, but I'm stuck on this one.

Doc8, I really don't see how asking a difficult question is "making trouble" in science. All science is the result of people asking difficult questions. And no, I'm not attacking evolution as a theory: it is, in my view, the most comprehensive, plausible and proven theory in biology. It's a pity its proponents are forced to be so defensive.

I'm familiar with how new genetic material can be incorporated into a cell in the case of, say, a bacterium acquiring antibiotic resistance through the insertion extra genetic material in the form of a plasmid, or through infection by a phage or virus. What I'm wondering, though, is what other mechanisms might be at play by which an organism can end up passing on more genes and base pairs than it started with.

This is not a Dorothy Dix question: I'm genuinely seeking some clarification.

Answer 1

Transposable elements, gene duplication and drift, unmatched crossover events.

A simple theoretical example: Start with a simple peptide hormone and a receptor. Duplicate both genes. Over time, the two mutate independently and now you have two hormones and two receptors capable of recognizing them. If it sounds implausible, look at the structural relationships among leuteinizing hormone, chorionic gonadotropin, follicular stimulating hormone and at their genetic coding.

Answer 2

I have to echo the recommendation to read novangelis' answer! Gene duplication, transposition, and other transcription errors are quite frequent ... often fatal, but not always, and occasionally useful. Once a gene gets accidentally duplicated, at first the duplicate gene codes the same protein, but it is free to get modified in all sorts of ways (because the original gene coding for the original protein is still around). This is how new genes for new proteins can evolve over time (fatal developments of this duplicate get weeded out quickly, neutral developments can hang around invisibly for generations, and any beneficial development will get propagated more widely).

For example, color vision in Old World primates probably arose from a gene duplication of the single opsin gene on the X chromosome of an ancestor. This is why humans have exactly the same three proteins responsible for red/green/blue color vision as Old World apes (African and Asian apes), but New World primates (those in S. America) who got isolated before this opsin duplication event, have only two of these (what some people call partially 'colorblind'). The fact that these two genes started out as duplicates on the X chromosome ... and are still located there ... is why this same 'colorblindness' affects men more than women (as men have only one X chromosome).

Answer 3

You answered your own question!! Think about sex determination in humans. We have the SRY region on the Y chromosome and all the other genes turned on by that region. You have one gene that contributes something to a process, then mutates, to contribute something slightly different and needed. So, it is selected to stay in the gang of genes doing the particular job. It is a snow ball effect, that can lead to more information in more organisms, responding in a more complex fashion to the environment

PS Novangelis has hit the nail on the head with his well researched answer. Much better than my hurried and clumsy response.

Answer 4

It is highly unlikely that a random addition to the genome will code for a new protein. However, you may be interested in chromosomal duplications, a process by which parts of a chromosome are replicated and maintained on that chromosome. When this happens, there is more than one copy of the gene on the chromosome, and over time, these two copies may lead to different forms of similar genes, called gene families. The globin genes are a familiar example.

Answer 5

Evolution in the human body does happen, maybe not on a huge scale, but on a small scale it does. Take for example those people that are makers of cholesterol, these people did eat something everyday of their life for many years (maybe hundreds of years).........so their body adjusted to make more cholesterol. Now-a-days these Cholesterol generators quit eating the stuff their ancestors use to eat, so now their bodies have excess cholesterol.

Answer 6

This is a fundemental flaw of evolution.
Richard dawkins was asked for an example of a mutation that had added genetic information.
After 10 seconds he asked for the camera to be turned off!
The clip on the link has been rather kind to him.

No such example has been forthcoming.

http://www.gospelcom.net/cgi-bin/hurl?f=aig/video/FrogToPrince.rm

Evolutionary arguments are easily refuted:
http://www.answersingenesis.org/home/area/RE2/index.asp

Answer 7

Simple. That doesn't happen. If it did happen and you could observe it happening, it would be evidence of evolution. Since it SHOULD happen but does not, it is one of the many, MANY similar missing observations that are strong proof against evolution.

Put another way. Mutation causes disease, not evolution. The product dies rather than reproduces. There are rare exceptions, but these never last more than a few generations. No exceptions.

Answer 8

Did you ever hear of "Sports"? I have no definitive answer for you. I think this question is to make trouble for evolution.