Answer to Question #163322 in Biology for Trix Wu

Question

While the alphabet has 26 letter, how is it possible for the DNA and RNA to code us with only 4 letters??

Answer 1

Although DNA and RNA use four letters (A, G, C and T or U) to encode the protein sequence, each amino acid in a polypeptide is encoded by a triplet of nucleotides - a codon, consisting of three letters in DNA or RNA. Three different nucleotides in a triplet give 64 possible combinations. These nucleotides combinations encode amino acids and stop codons. As a result, four letters in DNA and RNA are enough to encode all amino acids in any protein.