Genetic code.From the above that the synthetic DNA into mRNA in the mold to spread out, so the genetic information in DNA to mRNA for relay to the nucleotide sequence of different kinds of tide of mRNA, thus determines the sorts of amino proteins to synthetic. Because waiting for the amino to synthesize proteins, there are about 20 type defined in the mRNA codon is composed of how many Ning clinic o tide per codon, thus cover of amino 20 types.