How DNA ''knows'' wich phenotype it needs to be

[Luke321]

Hello everyone,

 

Recently I got very interested in Biology and especially genetics and evolution. But I have a question that I don't seem to get answered, or maybe I don't understand the answer enough, so I wondered if somebody could help me out?

 

So the question is how DNA "knows" wich phenotype it needs to be? What I understand from evolution theory (I'm still studying it so correct me if I'm wrong) is that organisms that adapt better to certain enviorment, are more likely to survive and reproduce, so there will be more organism with the certain gen that produces the favorable type of change. An example wich I saw in a documentary got me thinking. The example was a desert rat that first had a brown fur, the same as the sand, and when volcanic eruptions took place, and the soil became black rocks, it became black. I understand that the certain gen that produces a black fur is then favorable but how does the DNA "know" (I know DNA doesn't know anything like humans do but I don't have a better word for it now) to turn more black. It isn't true that the rats become purple and yellow and green and black, and than the black ones rats are better adapted so they survive, right? So how does the DNA know this? Or am I thinking about it in the wrong way?

 

I hope somebody can answer my question and correct me if I'm wrong in any of my assumptions.

[Strange]

It is because there is natural variation in the colour among the population. Those with genes for the darker fur are more likely to survive and reproduce. So it isn't that the genes change to what is required, just that the proportion of the "good" genes gets increased by selection.

[Luke321]

I understand,but it seems weird that in the beginning of that proces of change, the diffrences are so little. So It seems to me it wouldn't matter. I mean if one rat has a light color, and another rat has a slightly darker color, but still a fairly light color, comparing to the black surface of the ground, it wouldn't really matter for, for example an owl or an eagle to see them both fairly equally. I mean I can probaly tell the difference from a 100 feet or more.

 

So I understand the principle, but I question if, at least in some cases, it really matters?

[Strange]

It will only affect evolution if it matters. It only needs to provide a small benefit to cause a change in frequency (in the population) over several generations.

[Luke321]

I understand what you are saying. Small changes can have a big effect in a few generations or longer, even if they begin small. But doesn't it seem weird to you, in my example, that the change is so minimal, but still is the prefereble gene?

 

I know that that is what the theory says, maybe I'm more interested if anybody has ever thought about it?

[overtone]

 

 

I understand,but it seems weird that in the beginning of that proces of change, the diffrences are so little. So It seems to me it wouldn't matter.

Human perception as to what is "little" or not is completely unreliable. What things "seem" like to you is not a sound base for reasoning. Do the arithmetic, measure the advantage.

 

And all these variations compound, interact - some of the lighter rats are a bit bigger than others, right?

 

Also, little variations established by chance - because they make no difference, nothing culls them - provide the new grounds for further variation.

 

And so forth.

[Luke321]

I see my problem now, thank you!

[RyGuyFly]

Hi Luke. I am super interested in genetics and stuff too and I saw that same documentary about the mice living on sand and on volcanic rock. To answer your question the DNA does not know that black fur would be better for living on volcanic rocks. Basically the small changes in the DNA are just small variations that appear to do very little or nothing. But then occasionally there will be a change that will alter the survivability of the individual. His genes then get passed on to future generations.

 

So with the example of the mice. Its possible that the same population produced white mice but they would die off easier than the rest of the population and not pass on their albino genes. Whereas the black genes got passed on because the black mice had better survivability on the black rocks. If the mice were living on a white sand beach then maybe the white mice would have survived better. For example Google beach mouse, they are a light sandy color. Some species turn white only in the winter as in increases survivability in the snow. Google snowshoe hares.

 

also you might want to Google terms like founder effect, bottle necking, and genetic drift. I find these topics extremely interesting. there are some great youtube videos out there on the subjects too.

Edited August 31, 2015 by Ryan1234