Genome junk segments?
Mar 6, 2001 , Dov in biologicalEvolution
Re: Present State of Evolutionary Genomics
Re J.Whittfield's "How the sequence got the way it is" , at http://www.nature.com/nsu/010215/010215-1.html.
Quotes from this article : "Our chromosomes are stuffed with hitchhikers, 'mobile elements' that jump around the genome…." and .."These DNA parasites destroy and create." I find this acceptable. But when some other authors refer to "junk segments" I am irked.
In line with my concept that genes, not cells, are the historical base units of life (and that cells are evolutionary products of genes) I keep in mind that the one and only reason and goal of ALL cell-based life forms is the survival, and thus the replication, of its resident genes.
It stems from this, and thus it may also be impressed by the concluding paras of the above article, that the chromosomal symbiotic genes associations would reject what has a net endangering effect on them and would accept whatever would have a net benefit effect for the association.
21 01 2007, in Hypo forum
Probing the secrets of 'junk' DNA
Quote from the above report:
"…additionally puzzling, he said, is that in some instances enhancers can be located millions of nucleotide bases (units of DNA) away from the genes they regulate.
"Evolutionary studies based on comparing DNA from different species – humans, mice and other vertebrates – provide us with some clues on how to identify gene regulatory elements, but how to understand the function of gene regulatory elements based purely on their sequence has remained an open question," he said.
I suggest that whereas the position of an enhancer may be far away from the position of its master gene along the length of the denatured analyzed nucleotides' chain, these positions may be close to each other in the natural undenatured coiled chromosome state.
Additionally, the sequential contents-identities of genes and enhancers deciphered along the length of an uncoiled chromosome in present-day genomes may be different from those of their long-ago predecessors. Individual present human genes are now interdependent members of the genome's cooperative commune, which in the course of its evolution might have ejected genes or otherwise modified its gene-membership list or locations of its member-genes and/or enhancers.