The advantage of working with close primate cousins is that we canisolate truly relevant parts of the DNA and the changes involved. This item reports on current findings comparing us with Chimps andRhesus monkeys. There are obvious ways to expand this work but it iscertainly begun.
I do not know how far we are from completely understanding the roleof every molecule although it is obviously a long way. Yet it isbowing to systematic methods and I think that the exponential growthof computer power will overcome this daunting task far sooner than weimagine.
It is curious that the regulatory mechanism can be switched aroundso readily. Yet for rapid change to occur, that makes sense. Thecode itself does not change but the change agents do. This is thehidden hand at work and it has little to do so far with randomselection.
Humans, chimpanzeesand monkeys share DNA but not gene regulatory mechanisms
http://archaeologynewsnetwork.blogspot.ca/2012/11/humans-chimpanzees-and-monkeys-share.html
Humans share over 90%of their DNA with their primate cousins. The expression or activitypatterns of genes differ across species in ways that help explaineach species' distinct biology and behavior.
DNA factors thatcontribute to the differences were described on Nov. 6 at theAmerican Society of Human Genetics 2012 meeting in a presentation byYoav Gilad, Ph.D., associate professor of human genetics at theUniversity of Chicago.
Dr. Giladreported that up to 40% of the differences in the expression oractivity patterns of genes between humans, chimpanzees and rhesusmonkeys can be explained by regulatory mechanisms that determinewhether and how a gene's recipe for a protein is transcribed to theRNA molecule that carries the recipe instructions to the sites incells where proteins are manufactured.
In addition toimproving scientific understanding of the uniqueness of humans,studies such as the investigation conducted by Dr. Gilad andcolleagues could have relevance to human health and disease.
"Throughinter-species' comparisons at the DNA sequence and expression levels,we hope to identify the genetic basis of human specific traits and inparticular the genetic variations underlying the highersusceptibility to certain diseases such as malaria and cancer inhumans than in non-human primates," said Dr. Gilad.
Dr. Gilad andhis colleagues studied gene expression in lymphoblastoid cell lines,laboratory cultures of immortalized white blood cells, from eighthumans, eight chimpanzees and eight rhesus monkeys.
They foundthat the distinct gene expression patterns of the three species canbe explained by corresponding changes in genetic and epigeneticregulatory mechanisms that determine when and how a gene's DNA codeis transcribed to a messenger RNA (mRNA) molecule.
Dr. Gilad alsodetermined that the epigenetics process known as histone modificationalso differs in the three species. The presence of histone marksduring gene transcription indicates that the process is beingprevented or modified.
"Thesedata allowed us to identify both conserved and species-specificenhancer and repressor regulatory elements, as well as characterizesimilarities and differences across species in transcription factorbinding to these regulatory elements," Dr. Gilad said.
Among thesimilarities among the three species were the promoter regions of DNAthat initiated transcription of a particular gene.
In all threespecies, Dr. Gilad's lab found that transcription factor binding andhistone modifications were identical in over 67% of regulatoryelements in DNA segments that are regarded as promoter regions.
Theresearchers presentation is titled, "Genome-wide comparison ofgenetic and epigenetic regulatory mechanisms in primates."
Source: AmericanSociety of Human Genetics [November 06, 2012]
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