Genetic code does not contain ?

The information needed to direct the synthesis of protein is contained in the mRNA in the form of a genetic code, which inturn is transcribed from template strand of DNA and is therefore complementary to it. The genetic code is the system of nucleotide sequences of mRNA that determines the sequence of amino acids in protein.Codon is a sequence of three adjacent bases that corresponds to one amino acid. There are 64 possible codom sequences. Because four nucleotide bases A,G, C and U are used to produce the three base codons, there are therefore 64(43) possible codon sequences.Thymine is not involved in codons as mRNA does not contain thymine (codon is contained in mRNA).