Question

Codons with U or C as the second nucleotide, for example, tend to specify hydrophobic amino acids. Can you suggest a possible explanation for this phenomenon in terms of the early evolution of the protein synthesis machinery?

Answer 1

ANS .Genetic code -The relationship between the sequence of nucleotides on mRNA and sequence of amino acids in the polypeptide is called genetic code .

The codons are tripet , out of 64 codons,61 code for amino acids and 3 codons (UAA,UGA,UAG)donot code for any amino acid hence functions as stop or terminating codons.

one very important feature of genetic code is the codons with similar chemical properties often have similar codons.Codons with second nucleotide as U or C often tend to specify hydrophobic amino acids. In terms of early evolution of protein synthesis machinery it can be possible in the early cells the matching between codons and amino acids was less accurate as compared to present cells.This feature of genetic codon may has allowed the early cells to tolerate this inaccuracy by allowing a blurred relationship between sets of roughly similar codon aminoacids and codons