Alternative Mechanisms For Evolution?

[Cogwulf]

I have read recently that many scientists are beginning to believe that genes which control the activity of other genes are much more important in creating organisms than genes which create actual proteins. This adds another layer to the discussion about junk DNA because it means that junk DNA can be looked at as DNA waiting to do something rather than as DNA which does nothing

 

[Agent Intellect]

Was just sort of thinking about this today, and I wonder if there is some sort of evolution that happens within a single organism on a cellular basis.

Most people know about the bad transcription errors in cells that lead to cancer, but what about good ones? If a cell within our body had some mutation during transcription that was advantageous, for example, a liver cell that started synthesizing more peroxisomes, so that it was able to live longer and filter more toxins. Because of this, it could undergo mitosis before dying/apoptosis, and it's sister cells would also have a better chance of undergoing mitosis before dying etc etc.

In this case, evolution could happen to a single organism within the span of one lifetime - the biggest hole I can see is that, even if an advantageous mutation happened in one part of the body, that doesn't necessarily mean it will be passed on to the offspring. On the other hand, if an advantageous mutation happened in the gametocytes. The other hole is that for this sort of evolution to propagate to the offspring (like in the latter example) would require it would probably require a lot more chance then classical natural selection requires.

On the other hand, even if the traits from cellular evolution didn't get passed down, an advantageous mutation would increase the fitness of the organism and allow them to propagate their other genes more.

Anyway, just more of me "thinking out loud"...

 

[Agent Intellect]

Interesting article I just came upon (and decided, while interesting, didn't warrant it's own thread).

http://news.yahoo.com/s/time/20091024/hl_time/08599193175700

 

[Anling]

I have read recently that many scientists are beginning to believe that genes which control the activity of other genes are much more important in creating organisms than genes which create actual proteins.

The Hox genes are very important in how an organism actually develops. They determine when, for how long, and which genes get expressed.

This adds another layer to the discussion about junk DNA because it means that junk DNA can be looked at as DNA waiting to do something rather than as DNA which does nothing

This is true for at least some of the junk DNA. It can be seen in insects especially well. In the walking stick family there are several lines that lost wings and then gained them again. What happened was that the Hox gene telling them to activate the genes for wings got turned off, then later on in the family tree it got turned back on. Instead of loosing the genes for the wings themselves, just the expression of those genes changed.

Also, birds still carry quite a lot of the genes to make them look like their theropod ancestors. They've got the genes for teeth, long tails, and clawed fingers. But these genes are not expressed in them. We know they're there because some researchers turned them back on in some chicken embryos. I don't think they ever let any of them get to hatching point though.

Also, any stretch of DNA an organism is not currently using is free to mutate with impunity. That may take genes that used to be able to do something and make them nonfunctional, or simply tweak it a little for better or worse. If it ever gets turned back on, then natural selection can work on it. But natural selection can only work on what actually gets expressed.

 

[Agent Intellect]

The Hox genes are very important in how an organism actually develops. They determine when, for how long, and which genes get expressed.

Are Hox genes usually considered part of the "junk" DNA though? I admit I haven't done too much reading about the "junk" DNA, but don't expressor genes (like Hox genes) usually code for something that affects the way other genes are expressed (ie methylation) - the point being, expressor genes are not non-coding?

This is true for at least some of the junk DNA. It can be seen in insects especially well. In the walking stick family there are several lines that lost wings and then gained them again. What happened was that the Hox gene telling them to activate the genes for wings got turned off, then later on in the family tree it got turned back on. Instead of loosing the genes for the wings themselves, just the expression of those genes changed.

I wonder if there is some selection pressure for organisms to maintain unexpressed DNA - perhaps early on, organisms that maintained unused DNA from prior generations were able to evolve quicker then ones who did not, thereby propagating "junk" DNA friendly chromosomes into the later generations.

Also, birds still carry quite a lot of the genes to make them look like their theropod ancestors. They've got the genes for teeth, long tails, and clawed fingers. But these genes are not expressed in them. We know they're there because some researchers turned them back on in some chicken embryos. I don't think they ever let any of them get to hatching point though.

http://dsc.discovery.com/news/2009/03/05/dinosaur-chicken.html

Also, any stretch of DNA an organism is not currently using is free to mutate with impunity. That may take genes that used to be able to do something and make them nonfunctional, or simply tweak it a little for better or worse. If it ever gets turned back on, then natural selection can work on it. But natural selection can only work on what actually gets expressed.

Co-adaptation (1) (2) and paramutation of genes could still affect the selection pressure on unexpressed genes - if a non-coding gene is in some way 'linked' to a coding gene, there could possibly be selection acting upon the non-coding gene through it's partner.

But, I would agree - for the most part, non-coding DNA has no affect on the fitness of the organism, allowing more 'wild' mutation. I wonder if this could account for some of the punctuated equilibrium; at some point, an organisms offspring has some of it's non-coding DNA start coding, and it affects very large changes. Just a hypothesis anyway.

 

[merzbau]

Viruses, the most successful viruses do take a long time ot kill the host, if at all. For a virus, killing a host isn't necessarily self-defeating. Killing it very quickly before it can spread, is. Often, when we notice new viruses emerge, quite a few people die right away. Then, people live with it a little longer and/or it becomes milder. When Syphilis came to Eurasia, it killed people very quickly at first. Then, it adapted to new hosts and became a more drawn out disease. If one little cluster of viruses can find a host, multiply, spread to several new hosts, it is very successful.

delayed response, but you're right! thanks, that was something that's been bugging (pun unintended) me about viruses for ages.
wikipedia also mentions a theory that viruses are relatively benign in their host species, and become killers when they cross to a species that doesn't have a natural resistance to them. which would mean that the goal of a virus is to reach equilibrium within a host. in that light, even ebola sounds positively amicable.

one other thing that struck me about agent intellect's "horizontal gene transfer evolution" theory, was that it seems very like the same cross-pollenation action that bees and insects perform for plants.

 

[[SS].Invictus]

Please forgive me if what I type right now seems like I am being an ass;

B.U.T

Intelligence design is NOT an alternative at all; I.e, http://video.pbs.org/video/980040807/

Will write more soon.