Tag Archive | "genetic code"

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Genetic History: Some Have Made Their Mark

Posted on 15 January 2014 by Jerry

Genome sequencing is rapidly advancing our knowledge of genetic contributions to the human species.   Recent genetic studies indicate interbreeding between Africans who initially migrated around the world and made up the largest part of the modern human genome, with Neanderthals, Denisovans, and an as yet unknown branch of hominid that contributed to our genetic code.

This new knowledge is demonstrating the evolutionary tree of modern humans includes new ancestral groups.  We see their presence in our genetic code.  This is becoming readily apparent from largely mitochondrial DNA, as well as nuclear DNA, extracted from archeological sites widely distributed in Africa, Siberia, Northern Germany, and Eurasia.

A recent article in Nature shows a likely gene flow that puts the contribution of the unknown ancient population in perspective.  It is from a recent article in the January 2, 2014 issue of nature magazine by Ewan Birney and Jonathan K. Pritchard.  It contains a chart showing first the genetic input of an unknown archaic population was followed by the main human tree splitting into two, with modern Africans separated from Neanderthals and Denisovans and a later branching to two separate  directions for Neanderthals and Denisovans.

This article stated “One surprise was the first clear evidence for interbreeding between Neanderthals and modern humans; another was the discovery of a second type of archaic hominin in Eurasia in addition to Neanderthals.  This group has been dubbed Denisovans.”  Continuing, the article states, “Most provocatively, Prufer et al. find evidence for levels of gene flow into Denisovans of sequence that is different from that of any known group, implying that there is at least one more, so far undiscovered, archaic-hominin group.”

This new information suggests some unusual conclusions can be drawn.  We have dramatically expanded our abilities to extract genetic information from all sorts of ancient remains.  The genetic material used for these studies is from single individuals in the distant past in each population group.  It is clear their presence and existence is indelibly inscribed in our own genetic code.  This knowledge of them has survived the passage of time.  These individuals, who ever they were, have created a lasting impact.

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RNA at the Beginning

Posted on 11 December 2011 by Jerry

In beginning-of-life experiments scientists have looked for that first life that could form and retain a genetic code and replicate the code in another organism.  The farther back in the life process this discovery could be made, the closer humanity would be to understanding how life began.  Over the years many have speculated that before the first life as we know it there was a macromolecule ribonucleic acid (RNA) which developed these properties.  The theory holds that it evolved before deoxyribonucleic acid (DNA) which today is the main component of our chromosomes.

As reported in the April 8, 2011 Science magazine, researchers Aniela Wochner, James Attwater, Alan Coulson, and Philipp Holliger of the Medical Research Council Laboratory of Molecular Biology in the UK have created a very general and flexible RNA polymerase ribozyme that can synthesize a wider spectrum of RNA sequences. This is essentially an RNA macromolecule that has its own genetic information and can cause a chemical reaction that expresses its genetic code in another active RNA molecule.

This development adds significant support for the RNA-First hypothesis.  While not yet creating life in a laboratory, this does demonstrate an RNA macromolecule which has its own genetic code and can replicate it in another, different, RNA macromolecule.

Background: In Beyond Animal, Ego and Time, in Chapter 2: Life, Death, and the Biogenic Sphere there is a summarization of the various beginning of life experiments that led to the present view of the beginning of life.  On page 22 there is discussion of the theory that RNA is where the first self replicating entity evolved.

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