According to An Introduction to Genetic Analysis, Genetic code is the set of correspondences between nucleotide pair triplets in DNA and amino acids in protein. Can you explain what it correspondence in this regard? I don't understand why nucleotide pair triplet and not simply nucleotide pair? Is it mostly because DNA is ds?
You must know that there are two strands in DNA: “sense” strand and “antisense” strand. “Sense” strand has the same sequence as the appropriate mRNA. “Antisense” strand serves as a template for mRNA during transcription process. During translation this mRNA serves as a template for an appropriate protein. Each three nucleotide in mRNA corresponds one amino acid in forming protein. So each triplet in mRNA corresponds one amino acid, which means that each triplet in DNA eventually corresponds one amino acid. Nucleotide pair, in itself, cannot correspond any amino acid since this is only two nucleotides on different strands. Ribosome needs three nucleotides on one strand of mRNA to determine what kind of amino acid should be included in the growing polypeptide chain.