Posted on 01/15/2008 7:55:39 PM PST by neverdem
DR. FEERO is a family physician with a doctorate in human genetics from the University of Pittsburgh. He is a senior adviser for genomic medicine in the Office of the Director at the National Human Genome Research Institute.
Our understanding of the genome is changing rapidly and drastically.
For starters, the Human Genome Project has revealed that humans are, on a numerical basis, genetically less complex than a mustard plant (Arabidopsis). In fact, our genome contains between 20,000 and 25,000 sequences suggestive of “genes” encoding proteins, whereas Arabidopsis contains about 27,000. If that doesn't make much sense to you, don't worry, it didn't make any sense to many of the scientists working on the human genome either. Empirically, most of us are far more complicated than a mustard plant. This paradox harkens back to one of the teachings of distant biology and genetic courses, written by our parents' generation. To paraphrase many texts: “About 98% to 99% of the human genome appears to be junk, leftover from evolutionary dead ends.” Any student of biology could spot a problem here: Evolution tends to trim baggage and inefficiencies. Why would we use only 1% of our genetic material after a few billion years of trimming the excess?
Genome scientists recently have completed the first phase of a massive collaborative project, supported by the National Human Genome Research Institute (NHGRI) of the National Institutes of Health, called ENCODE (Encyclopedia of DNA Elements). Initiated in 2003, ENCODE was designed to enhance our understanding of the functional anatomy of the raw DNA sequence revealed by the Human Genome Project.
The first phase focusing on 1% of the genome, completed in June 2007, has shown that all that junk is not junk after all. Our genome is a complex ecosystem with a wide variety of different types of DNA elements, not simply genes encoding proteins. Much of it appears to play a role in determining which genes are expressed, in what order, and at what levels. Substantial portions of our DNA encode information for the production of small RNA molecules that never become translated to proteins, but rather fold up on themselves and act in concert with peptides as regulators of gene expression. Some of these molecules likely act as RNA-based enzymes. Very long stretches of DNA that don't seem to code for any proteins, and therefore would not be predicted by previous models to be highly conserved by evolution, are highly conserved. In contrast, regions that previously would have been predicted to be conserved turn out not to be under as much evolutionary constraint as had been thought.
How about those mustard plants? The emerging model is that human genes don't ascribe to old “one gene, one protein” rule, but are much more akin to Russian nesting dolls. Genes are inside of genes, using alternate promoters, start sites, splicing sites and stop sites. Remember that DNA is double stranded? There is evidence that there are overlapping genes that run on opposite strands, encoding proteins of different functions.
Recall that RNA molecules are translated to form proteins? It turns out that seemingly unrelated RNA molecules can be assembled (trans-spliced) to form templates for entirely new proteins. To further complicate this picture, elements in the DNA known as pseudogenes exist, which, save for minor variations, look exactly like other functional genes.
ENCODE and related results suggest that these pseudogenes are numerous and that they may not be as transcriptionally silent as once believed. Overall, the first phase of ENCODE has demonstrated how little we really know about the human genome. NHGRI has pledged more than $80 million dollars in grant awards to flesh out our understanding of the functional elements in the 99% of the genome not covered in the pilot phase of ENCODE.
Well, that goes without saying. ;o]
*snirt*
My lesser genome sized brain figured it out. I’ve been vegetating lately with a cold, but have not yet devolved into a plant.
May not be long. Hope all’s going well for you in the New Year.
Or 'Nature.' Sure seem to be a lot of Gaiaists out there....
There was a time when God (appropriately) got the compliments/credit.
Agree with your comment.
It is interesting you use a tomb as your analogy. I'll ponder your meaning with grave consideration.
Here’s hoping all goes well for you, too, in the New Year! And watch that cold - some have the nasty habit of evolving into pneumonia.
Thanks
I'm suspect as time goes by, "science" will experience even greater surprises in the complexities of His creation. Truth be known, if they could see the totality of it all, they would likely be scratching their collective heads wondering why they couldn't see it before.
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