The Jaina Doctrine of Karma And The Science Of Genetics: Genetic Codes

Genetic Codes

The importance of DNA lies in its ability to control the formation of other substances in the cell. It does this by means of so called genetic code. When the two strands of DNA molecule are split apart, this expose the purine and pyrimidine bases projecting to the side of each strand. It is these projecting bases that form the code.

Fig. 30: Arrangement of deoxyribose nucleotides in DNA.

Research studies in the past few years have demonstrated that the genetic code consist of triplets of bases—that is, each three—successive bases is a code word. The successive triplets eventually control the sequence of amino acids in a protein molecule during its synthesis in the cell. Note in figure 30 that each of two strands of the DNA molecule carries its own genetic code. For instance the top strand reading from left to right, has the genetic code CGC, AGA, CTT the triplets being separated from each other by the arrows. As we follow these genetic codes through figure 31, 32. We see that these three respective triplets are responsible for successive placement of the three amino acids proline, serine and glutamic acid in a molecule of protein. Fig. 30: Arrangement of deoxyribose nucleotides in DNA.^[69]

There are more than 20 different amino acids and only four bases, so the code cannot be based on a one-to-one correspondence between amino acids and bases. Biochemical investigations have revealed that the mRNA code is a triplet code that is, each successive frame of three nucleotides. Sometimes called a codon, of the mRNA correspondence to one amino acid of the protein. This rule of correspondence is the genetic code. The genetic code consists of 64 entities—the 64 triplet possible when there are 4 possible nucleotides, each of which can be at any of three places (4 x 4 x 4 = 64).^[70]

Table-2: The genetic code is a triplet code, consisting of 64 entries. Each triplet, called a codon, represents a frame of these nucleotides (U = uracil, C = ctyosine, A = adenine, G = guanine) on messenger RNA. At least one codon, and usually more than one, codes for each of the 20 amino acids. A few triplets signal the "stop" of protein assembly and at least one—methionine—may signal the "start".

Amino acids specified by each codon sequence on mRNA key for the above table:

A = Adenine, G = Guanine, C = Cytosine, T = Thymine, U = Uracil.

Fig. 35: I, II, III bases of codons

Fig. 36: Ribonucleic Acid Structure

DNA transfers information to mRNA in the form of a code defined by a sequence of nucleotides.