The cerebellum will be shown to be the graveyard of the "Junk DNA" misnomer
Misnomer: " Junk Gene * ":
98.7% of the Human DNA used to be called "Junk DNA" for lack of a clear, much less mathematical, explanation of the role of so-called "non-coding" DNA sequences.
Below, the "Junk DNA" misnomer is analyzed. The Cerebellum will be shown to be the graveyard of this "Junk DNA" misnomer
*This pejorative name for the silent majority of DNA was coined by Suumu Ohno in the early 70’s See: Kuska B Journal of the National Cancer Institute 90, 1032 (1998)
Nobel Laureate Gilbert: "Junk Gene", and Exons-Introns
(Excerpts from New York TImes, 1996)
In a basement room at Harvard University's science center one morning a few weeks ago, Dr. Gilbert was at the blackboard, describing the puzzle to nonscientists. He noted that the genes in modern animals were stored in the DNA not as nice readable texts but as choppy fragments that the cell's machinery must stitch together. That curious arrangement is one major clue. Another is that some 95 percent of a person's DNA does not code for genes at all. It seems to be just gibberish, or junk DNA.
Genes in pieces and huge stretches of junk? "At first glance, it is peculiar," Dr. Gilbert told the bleary-eyed students. "Then, at second glance, it is even more peculiar".
I think it's one of the major unsolved mysteries of the basis of life."
Dr. Gilbert and his colleagues have sketched out a theory of how it all may have happened and what the first genes were like. It was he who coined the terms for the interrupted pattern in which genes are stored on the DNA; the working parts he called "exons" and the regions in between, which the cell has to splice out, he termed "introns."...
As Dr. Philip Sharp, a molecular biologist at the Massachusetts Institute of Technology, puts it, few scientists are willing to spend time on so vexing a puzzle. "Yes," Dr. Sharp said, "it is very difficult. It may even be unsolvable. That won't stop Wally Gilbert, of course." Dr. Sharp, who shared a Nobel Prize in Physiology or Medicine in 1993 for finding introns, one of the discoveries that sent Dr. Gilbert off on this track, said the ideas that Dr. Gilbert put forward "captured the imagination of the field, and still has it, I think."
If Dr. Gilbert's approach is valid, in principle of the entire history of life on earth could be inferred from the DNA of modern genes. His theory is an effort to figure out how, in the primordial waters where life began, the earliest genes were assembled. A modern gene is a chemical text with a thousand of letters. For such a structure to evolve at random would be a lengthy process.
Instead, Dr. Gilbert suggests, the first genetic elements were simple modules, the forerunners of today's exons, and the exons were then mixed and matched to build up the lengthy chains that make longer and longer genes. By analyzing the structure of contemporary genes, it should be possible to discern the ancient modules within.
For the modules to mix and match, Dr. Gilbert believes, they would have needed strips of extra DNA, like the leader on a reel of film, so that two modules could be spliced together without risk of cutting into their genetic message in the process . The introns, the elements interspersed between the coding regions of genes, are in this view related to the ancient leaders that enabled the modules to be assembled. Critics say the theory leaves some awkward issues unexplained. Introns are found in the DNA of plants and animals but not in that of bacteria. So did bacteria lose their introns or never acquire them?
Dr. Jeffrey D. Palmer at Indiana University and a few other experts in molecular evolution suggest that Dr. Gilbert's theory is wrong. They say that the introns and the shuffling of genetic modules were mechanisms that did not arise until two billion years after life first began. And, they regard the introns not as clever Tinker Toy construction elements, but as just what they appear to be, pieces of junk DNA left over from billions of years of evolution.
Noting that bacteria, presumably more primitive than plants and animals, do not have introns in their genes, they say it is more reasonable to assume bacteria never had introns than that they had and later lost them.
But bacteria may have streamlined their genetic material by shedding their introns leading ot the "pleasantly perverse" conclusion that humans can be considered as "less evolved" than bacteria, Dr. Gilbert said with a grin. "maybe we are not in all ways at the pinnacle of evolution, as people like to think," he said. And worse, maybe nature will evolve right past humans and their junk-laden genomes in the future.
Noncoding DNA makes up a significant portion of the total genomic DNA in many eukaryotes. For example, older sources estimate 97 % of the human genome to be noncoding DNA (Yam 1995), while the recently published sequence data increases the estimates to 98.7% noncoding DNA (Venter JC, Adams MD, Myers EW, Li PW, Mural RJ, and 269 other authors. 2001. The sequence of the human genome. Science 2001: 291:1304-1351.). These estimates present problems for both intelligent design and naturalistic/evolutionary models of the history of life.
Above, the "Junk DNA" misnomer was reviewed. The Cerebellum will be shown to be the graveyard of this "Junk DNA" misnomer in the forthcoming"Special Issue " of "The Cerebellum"