2/08/2009

Such a Degenerate!!!


Don't worry, I'm not going to talk about the 90,000 sex offenders kicked out of MySpace. I'm actually going to mention something that puzzled me when I was in my undergrad years. The Degenerated Genetic Code.
Our genetic code, or set of instructions coded in the DNA, is what alllows each cell in our body to synthesize proteins. Proteins are molecules of life formed by a chain of aminoacids that acquire a specific shape and function by folding its components into intricate 3d structures.
DNA (Deoxyribonucleic acid) is composed of nucleotides, or genetic "letters": A (Adenine), T(Thymine), C(Cytosine), G(Guanine). Three of these letters together form a codon (triplet), or "genetic word". The meaning of each of those words is an aminoacid. When a long string of "genetic words" are read, a long chain of aminoacids is produced. This is done making a usable copy of DNA, called RNA (Ribonucleic Acid), a template made from DNA that can be read and then destroyed. The differences between DNA and RNA are: DNA is a double chain molecule, whereas RNA is a single chain molecule. DNA contains the nucleotides: A, T, C, G. in RNA, the nucleotides are: A, C, G and U (Uracil). Uracil replaces T in RNA.
It was well known that the positioning of each genetic letter (A, T, C, G) in the triplet or codon, would determine a different type of aminoacid. However, it had been found that when the first two letter positions remained constant, and only the third letter was changed, it could be observed that the aminoacid produced was the same. This is called Degenration of the Genetic Code.
However when the first or second letters were replaced or changed, a different aminoacid was produced, and the resulting protein usually was defective, or misfolded, useless for its original purpose in any case.
This is something like genetic synonimity, if the term can hold the analogy. Because more than one triplet could "mean" or produce the same aminoacid.
I just came across a report from the American Journal of Human Genetics that takes this degeneration to a research study that found that 1 in 200 genes can be superfluous or dispensable.
Here is the link to the article, take a look at it.

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