Posted by: Randall Niles | May 6, 2010

Genetic Code is Far from Random

Here’s a thought… If the latest, scientific, peer-reviewed research (see below) indicates that the genetic code did not evolve randomly, then what is the origin of genetic information…?

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SCIENCE: Salk study: The genetic code isn’t random

By Bradley J. Fikes, NCTimes.com | Posted: April 18, 2010

DNA makes RNA, which makes proteins. That’s the so-called “central dogma” of biology, in which the genetic code specifies what gene sequence equals which protein.

But is this universal code of life arbitrary? Could other codes have emerged?

Scientists from the Salk Institute have found evidence that the code is not arbitrary, but in part determined by how RNA interacts with the building blocks of proteins, called amino acids.

The findings by Salk researchers Lei Wang and David B.F. Johnson were published last week in the Proceedings of the National Academy of Sciences.

To explain the discovery, some biological background helps:

Proteins are made up of 20 amino acids. Each amino acid is specified by at least one RNA “codon,” a sequence of three nucleotides. Because there are four nucleotides, the triplet combination 4-by-4-by-4 makes for 64 possible amino acids.

With only 20 amino acids, the code of life is redundant. Some amino acids are represented by more than one codon. Other codons are reserved for “punctuation” that represent the beginning or end of a protein sequence.

The question vexing biologists is whether the codon/protein code has to be the way it is for reasons yet unknown, or simply evolved that way. Since life arose billions of years ago, direct evidence isn’t available.

So the Salk scientists focused on ribosomes, organelles that make proteins from amino acids. Ribosomes are made up of proteins and show evidence of being ancient structures from early in the evolution of life. The researchers reasoned that the ribosomes would provide evidence of the genetic code’s origin.

The researchers studied bacterial ribosomes and two kinds of RNA, called messenger RNA and transfer RNA, that carry the genetic code in a kind of molecular bucket brigade.

Messenger RNA copies the code of DNA in the nucleus and takes it to the ribosomes, located outside the nucleus. Then transfer RNA picks up each codon sequence as an “anticodon,” like a photographic negative. Finally, the anticodon picks out a specific amino acid.

The researchers found evidence of preferential pairing between certain anticodons and amino acids. In other words, the current code didn’t evolve randomly.

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Keep Thinking,

Randall Niles

For more on the Salk study, please see: http://www.salk.edu/news/pressrelease_details.php?press_id=417

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Responses

  1. this is very interesting ….have you heard of

    David VanKoervering?

    He is a quantum physics scientist…..who created the lazer CD….and he tells us about DNA coding and the frequency of God…..it is quite fascinating….

    you can see him on YOUTUBE….

  2. I’ve been trying to find information about this for a while. An interesting article, available online, is “On the translation system and the genetic code in the RNA world by means of natural selection, exaptation, and subfunctionalization,” by Wolf and Koonin. The authors (traditional biochemists, not Intelligent Design adherents by any means) acknowledge that “The origin of the translation system is, arguably, the central and the hardest problem in the study of the origin of life, and one of the hardest in all evolutionary biology.” . . . . “The origin of translation appears to be truly unique among all innovations in the history of life in that it involves the invention of a basic and highly non-trivial molecular-biological principle, the encoding of amino acid sequences in the sequences of nucleic acid bases via the triplet code. This principle, although simple and elegant once implemented, is not immediately dictated by any known physics or chemistry (unlike, say, the Watson-Crick complementarity) and seems to be the utmost innovation of biological evolution.”

    And most interesting: “There is, however, a crucial snag about these models: they all rely on a pre-existing translation system. And the origin of the translation system is far from being a trivial matter. The main difficulty is not even its complexity per se but the necessity to invent a new principle, that of the genetic code, the correspondence between the a priori unconnected sequences of nucleotides and amino acids. It might not be much of an exaggeration to note that, at least, at first glance, the origin of the translation system evokes the scary specter of irreducible complexity.”

    In other words, how did the cell’s factory mechanisms learn to “read” genetic code, and what do we mean by “reading” it anyway? I take it we have no notion of a direct chemical pathway from the DNA code sequences to the amino acids they represent. This seems like an awfully interesting black box, and one I’m surprised not to see mentioned and argued about more often.


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