Initiation codon is

AUG which codes for methionine (Met) is used as start signal in protein synthesis. It is the most common chain initiation codon. In prokaryotes, the codons GUG and UUG are also employed in instances as start codons. Three triplets,UAA (ochre),UAG (amber) andUGA (opal) do not code for any amino acid and are callednon-sense codons. Their function is to terminate the message for gene controlling protein synthesis. Non-sense codons are also calledchain termination codons. UUU (uracil) codes for phenylalanine.