Tuesday, November 11, 2008

Genes — the 1 percent ‘solution’

Individualized genetic medicine? Not so fast there

Yes, that’s right.

The “binary” bits alleged to be the centerpiece of human heredity, beloved of evolutionary biologists, population geneticists, and above all, capital-letter Evolutionary Psychologists, in reality are only the 1 percent solution of heritability. Elementary!

As to WHY the gene is only the “1 percent solution,” here’s the details of the latest research.

First, one strand of DNA may code for several different proteins. (In a process known as alternative splicing, a cell can select different combinations of exons to make different transcripts, the story notes.)

Second, said “gene” can combine with several other different genes, in different situations, to produce yet more different proteins.

Third, genes often encode for RNA, not proteins.

So, throw out the 1 gene = 1 protein idea.

Beyond that, “genes” may make up as little as 1 percent of DNA. “Junk DNA,” which more and more is proving itself to be anything but junk, makes up much of the remainder.

And, non-coding introns can lie in the middle of a stretch of DNA that makes up a single coding exon.

Also, some DNA, such as methyl caps, and histones, controls whether or not an exon can even be expressed, or how. They’re part of “epigenetic marks,” an area of DNA far more poorly understood than genes, as traditionally described. And, it gets fun with them:
When an embryo begins to develop, the epigenetic marks that have accumulated on both parents’ DNA are stripped away. The cells add a fresh set of epigenetic marks in the same pattern that its parents had when they were embryos.

This process turns out to be very delicate. If an embryo experiences certain kinds of stress, it may fail to lay down the right epigenetic marks.

But, that’s not always the case. Sometimes, epigenetic marks can be inherited.

And, in a bit of quasi-Lamarckianism (though not quite as much so as prions), it takes RNA to guide these markers to the right spot on DNA.

And, if that’s not enough, studies of micro-RNA and half a dozen other “non-basic RNAs” show even more the role RNA plays, no subservience to DNA involved, in cellular development

So, this all his tie-ins for our commercial, chemical modern world.

Very preliminary research indicates that chemicals that appear to cause “genetic” damage may well be causing epigenetic damage instead.

That, in turn, throw the whole biotech tout sheet of “the promise of genetic medicine” into a big kink.

And, we haven’t even talked about the amount of viral DNA stuck inside yours and mine.

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