Why there's only 20 types of amino acids? exact answer and due in 10mins today

The genetic code is the universal language that relates base triplets in DNA to amino acids in proteins. ... Subtracting for a necessary stop codon, organisms could code for up to 63 different amino acids. One could argue that 20 is simply good enough, but several species use up to 22 residues to synthesize proteins.

Explanation:

The 20 amino acids that are found within proteins convey a vast array of the precise amino acid content, and the sequence of those amino acids, of a specific protein. Proteins not only catalyze all (or most) of the reactions in living cells.