In genetics, a nucleotide refers to the basic units that form genetical material. On the other hand, a codon refers to a sequence of three nucleotides in the mRNA or messenger RNA which are a set of molecules that take genetical information from ADN to the ribosome of the cell. This implies in the case of a 12 mRNA codons there are 36 nucleotides as each of the codons contains three nucleotides which means by multiplying the number of codons by three (number of nucleotides) it is possible to know the total number of nucleotides in an RNA sequence or in this case 12 (codons) x 3 (nucleotides) = 36 nucleotides.