Genetic code is a triplet code:
In During translation, the series of an mRNA molecule is read from its 5' end through ribosomes that then synthesize an appropriate polypeptide. Together in prokaryotes and in eukaryotes the DNA sequence of a one gene is colinear with the amino acid sequence of the polypeptide it encodes. Alternatively, the nucleotide sequence of the coding DNA strand, 5' to 3', specifies in specifically the similar order the amino acid sequence of the encoded polypeptide N-terminal to C-terminal. The relationship among the nucleotide sequence of the mRNA and the amino acid sequence of the polypeptide is known as the genetic code. The series of the mRNA is read in sets of three nucleotides called codons, by each codon specifying a particular amino acid that was shown in the figure. Moreover, three codons, UGA, UAG and UAA, do not encode an amino acid. Whenever one of these codons is encountered through a ribosome, it leads to termination of protein synthesis. Thus these three codons are known termination codons or stop codons. The codon AUG codes for methionine. While methionine is found at internal positions in polypeptide chains all eukaryotic polypeptides also begin with methionine and all prokaryotic polypeptides begin with a modified methionine (N-formyl methionine;). Thus, the first AUG codon that is read through the ribosome in an mRNA is known as the initiation codon or begins codon