Junk DNA.........?

Question

Darwins theory says that if a mutation is not favorable, it will be omitted. This obviously happens at the genetic level. So why do we still carry junk DNA around? If the simplest answer is usually the correct one then I would think that junk DNA is not spent cartriges, but more like blank checks. Are there any known correlations between junk DNA and random genetic mutation? Your' thoughts?

Answer 1

Mostly, it is not really useless. Much is possibly essential, and it would include DNA sequences involved in regulating the polypeptide - coding sequences. For a bit of extra discussion of that idea, see:

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http://www.abc.net.au/rn/science/ss/stories/s841482.htm

The Science Show (Australian ABC)

"Genes & Junk
Saturday 3 May 2003

Summary

Junk DNA. We all have it, in fact, 95% or more of our genetic material is junk. Plant geneticist Ian Godwin explains why."

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Also, I want to explain and speculate a bit:


There is a general principle called "the parsimony of Nature", that works against organisms carrying loads of useless junk attributes. You might search on that phrase, if you like. However, our cells can "afford" to carry pseudogenes; superseded and duplicate copies of "real" genes. This type of "junk" is handy, as a place to "try out" new mutations. (I am being a bit anthropomorphic, here!)

If the mutation has no effect, or makes the junk even more wrecked, well ... no sweat! It was just a bit of spare DNA, that can be stored away. If it happens to have useful properties, then ... whoa! the cell can benefit. That organism will do better than the rest. The junk has found a use, and will be selected for.

Many genes have extensive homology with other genes. They may have been "junked" spare copies (duplicates) that were re- modelled, in a way similar to what I just described.

Answer 2

First, you misstate Darwin's principle. The survival of the fittest is the usual expression, but that is only with respect to mutations that make a difference in the environment the species is in or adapting to. Nature has many examples of mutations that made no difference to survival and so continue, even though they confer no benefit.

We do not know enough about DNA to call any part of it junk. We can only say that long sections of DNA have no expression and therefor no use currently. Whether some random virus introduced a useless section, or a useless section underwent a mutation, or has remained unchanged, we will only know in the distant future.

No researcher will spend time and money on unexpressed sections of DNA until and unless there is a good (read, profitable) reason to do so.

Answer 3

I think there is a correlation, but junk DNA, introns/exons, and noncoding sequences are things that scientists are still trying to figure out... my thought is that Darwin's theory came before much of the real processes of DNA function were even known, therefore how can it explain everything we know about DNA? Darwin was useful for postulating natural selection but I don't take everything he says as fact.

Answer 4

I'm not exactly sure if this is going to answer your question, but sometimes mutations aren't random, think of the effects of smoke and alochol though a fetus, I am not sure if this would qualify as a genetic defect (although I be live it can be argued). Other things can cause mutation such as radiation.

Answer 5

If Darwin's theory is true why dont we have monkeys turning into humans no a days? On which basis the development of a species, if it is on the surroundings then why do we find a diversity of creatures on the same island??

Darwin's theory is false. All of its proofs are circumstantial and exclusive to it.