>stromme@mi.uib.no
>
><< I asked a similar question the other day, but no answers yet so I'll
> repeat it here: How can it be known that this DNA "is not used by
> organisms"? Is current understanding of genetics really that good?
> >>
>
>The short answer, No. Like most of science, it humbles.
(Snip)...
>
>There are some explanations, but the point is that we really
>don't understand that much about the system as a whole.
>Isolated parts, extrapolations, but there is a long long way
>to go.
>
>by Grace alone do we proceed,
>Wayne
I happened to be reading a paper relevant to this question, so here is a little more info (Nature Genetics 19:19 1998). It was recently estimated that 35% of the sequence of the human genome is composed of mostly "dead" transposable DNA elements. (For comparison, the functional protein coding regions comprise about 3%.) They are dead in the sense that they have many mutations, truncations or rearrangements that make them unable to express functional proteins or transpose (cut or copy themselves and insert at a new location) again. However, there are a few that are intact and still "jump" from time to time. This is known because there are (as of 1998) 19 known cases of disease caused by a new (not present in either parent's DNA) insertion of a transposable element into a gene. Most of these were germline insertions causing potentially heritable diseases, but a few were somatic insertions contributing to cancer development.
It would pretty hard to argue that all these thousands of defective insertion sequences in our genome have any design as to where they are, or that all have functions. However, a few of them do seem to have taken on a function. One class of elements are the endogenous retroviruses. Glenn Morton posted some material recently on the fact that some of these are present at exactly the same position in higher primates and humans, which is a very strong argument for common descent. Retroviruses contain a gene called 'env' which codes for the envelope protein that mediates fusion of the virus with the cell membrane to allow entry. The env protein of an endogenous retrovirus was recently found to be expressed in the human placenta and apparently contributes to the mass cell fusion that occurs in cells at the interface of the placenta and the uterus.
This kind of thing contributes to the belief by molecular biologists that usually mutations are neutral (like the insertion of most of the endogenous transposable elements) or detrimental (like the disease causing transposon insertions), but occassionally "random" changes result in something beneficial (like the env protein in the placenta.) I don't think this kind of thing rules out the possibility of invoking design, but there is a large component of apparent randomness in biology, and it has to taken seriously. On the other hand, as we know from human examples,design doesn't have to be perfect design to be recognized as such, and this should be remembered by those who feel a need to find a function for everything.
Somewhat along this line, I would be interested to hear what the ID camp has to say about the entities that appear to be both "irreducibly complex" (by their calculations) and examples of natural evil (like the AIDS virus or the pathogenicity genes of bacteria.) The AIDS virus appears to be very cleverly designed to cause devastating disease and to be resistant to any definitive treatment or vaccine. Virologists laugh at the conspiracy theory that it was constructed in a military lab. Even after billions of dollars of research on it, no one knows anywhere near enough to design something like that from scratch. So, did it come about by randomly picking up cellular genes, or does the Devil get to design things, too?
Just some bait to stir up a feeding frenzy,
Preston G.
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