Genome complexity: mechanism stopped evolving (Introduction)

by David Turell , Friday, May 06, 2016, 15:05 (3124 days ago) @ David Turell

The general pattern of how the genome works was established at the beginning of life and stopped changing more than 3 billion yeas ago:-http://motherboard.vice.com/read/why-did-the-genetic-code-of-all-life-on-earth-suddenly-stop-evolving-"All life on Earth exists thanks to a universal genetic code. This biological rulebook tells our cells how DNA should be translated into life-supporting proteins, without which we couldn't survive. -"Even though the genetic code commands a seemingly immeasurable number of organisms, it also binds us all together as descendents of a shared ancestor—a lingua franca for life.-"Yet for all of its diverse and essential properties, the genetic code is static. For some reason unknown to scientists, approximately 3 billion years ago it simply stopped growing. Instead of expanding to encode new combinations of amino acids, and potentially new life, it stagnated at its current size and function. But a new study published today in the journal Science Advances offers an explanation for the genetic code's mysterious evolutionary limit.-"A team of geneticists discovered that several billion years ago, the genetic code reached a point of self-preservation. Namely, it could continue evolving and risk mutating the building blocks of life it was responsible for creating, or it could remain limited, albeit functional.-***-"Over millennia, the genetic code evolved to contain “codons” of three nucleotides, which transfer RNA (tRNA) translate into a 20-letter chain of amino acids, leading to the creation of basic proteins. However, at some point in history, transfer RNA hit a functional limit to the number of amino acids it was able to successfully interpret into proteins, the study found. It was at that point the genetic code, and the complexity of organic life, stood relatively still.-"Any more than 20 amino acids, and the machinery of gene expression got confused. The results of such erroneous translation were constant mutations "with catastrophic consequences,” according to Ribas.-"While the expansion of the genetic code allowed for new tRNA creation, the particular L-shaped cavity of ribosomes—the part of the cell where protein is actually constructed—ultimately allowed for very little variation. If tRNA molecules didn't adapt to accommodate the specific needs of the ribosome, the efficiency of protein synthesis would be vastly compromised, and fatal for life.-“'There came a point when nature was unable to create new tRNAs that differed sufficiently from those already available without causing a problem with the identification of the correct amino acid. And this happened when 20 amino acids were reached,” Ribas explained."-Comment: The genome reached a practical limit to its complexity, is a reasonable explanation. That all life uses the same system means evolution was organized from the beginning by starting at one point. God's management is suggested.