The DNA, mRNA and tRNA are the essential nucleic acids that initiate protein synthesis. The DNA contains the genetic code of our human body in the form of chromosomes. It is composed of nucleic acids like uracil (U), guanine (G), adenine (A) and cytosine (C). The messenger RNA or mRNA carries this code called codons expressed in three-letter codes. Each amino acid has its own assignment of code. The mRNA carries this code to the ribosome which is the site for protein synthesis. The translational RNA or tRNA contains anti-codons to translate the codes in the mRNA into amino acids that link together to form proteins.