Question

Why do you think Gamow said that translation was just a cryptography problem? How many possible codons could you get if the genetic code was based on: a. One letter? b. Two letters? c. Three letters (as it actually is)? d. Four letters?

Answer 1

Gamow and his fellow scientists used a method called crypto analysis, known as neighbor distribution plots deployed of statistical analysis of known protein sequence experimentally.

Gamow and scientists used Brenner's table which shows neighbor distribution in a grid comprising of all 400 (20 * 20) possible amino acid pairs. So, Gamow said translation is just a cryptography problem.

- We have 4 nucleotides A,G,C, T.

We have 20 aminoacids to code for with 4 nucleotide combinations.

If we use 1 letter codons we could only code 4 amino acids following the rule 4ⁿ=4¹=4. (where 4= no. of nucleotides, n=no. of letters in codon).

If we use 2 letter codons we could only code 16 amino acids following the rule 4²=16.

If we use 3 letter codons we could code for all the 20 amino acids. But according to the rule 4ⁿ=4³=64. We could code for all amino acids where few codons code for a single aminoacid. Also, 20(no. of aminoacids)*3=60, which is nearer to 64 this happened because more than one codon codes for single aminoacid.

If we use 4 letter code we are produced with 256 nucleotide pairs according to rule 4⁴=256.We cannot acommodate 20 amino acids in such a huge possible combination pairs of 256 codons.