Which statement best explains why there are 64 possible codons in the genetic code and only 20 amino acids that make proteins of living organisms on earth? a) several codons code for the same amino acid. b) each codon can code for several amino acids. c) many other amino acids are made but do not form proteins. d) stop codons make up many of the remaining base sequences.

Codons are three letter genetic words: and the language of genes use 4 letters (=nitrogenous bases). Hence 64 words are there in genetic dictionary, to represent 20 amino acids that the biological organisms use.

And you must note that more than one codon may code for the same amino acid. This is referred to as degeneracy of the code.

For example, three amino acids are coded by any of six different codons, and that alone uses up 18 of the 64 combinations.

Three of the codons are stop codons.

They do not code for any amino acid.

Instead, they act as signals to end the genetic message carried by messenger RNA .

The number of amino acids coded by codons is

1 codon×l2 amino acids=ll2 codons
2 codons×9 amino acids=18 codons
3 codons×1 amino acid=X3 codons
4 codons×5 amino acids=20 codons
6 codons×3 amino acids=18 codons
3 stop codons
—————————————————————————lTOTAL=64 codons