Q. How do nucleotides of mRNA chains encode information for the formation of the amino acids sequences of a protein?
There are only four types of nitrogen- containing bases that can compose RNA nucleotides: uracil (U), adenine (A), guanine (G) and cytosine (C). Amino acids however are 20 different ones. Considering only one nucleotide a 1:1 coding it would be impracticable to codify all amino acids.
Considering two nucleotides there would be an arrangement of 4 elements, 2 x 2 resulting in a total of only 16 possible codifier units (4 x 4). Nature may know combinatory examination since it makes a genetic code by arrangement of the 4 RNA bases, 3 x 3, providing 64 different triplets (4 x 4 x 4).
So each triplet of nitrogen-containing bases of RNA codifies one amino acid of a protein. As these triplets appear in sequence in the RNA molecule, chronological amino acids codified by them are bound together to make polypeptide chains. For example, a UUU sequence codifies the amino acid phenylalanine, as well the UUC sequence the ACU, ACC, ACA and ACG sequences codify the amino acid threonine and so on for all possible triplet sequences and all other amino acids.