Fundamentals of Molecular Biology - V.I. Rezyapkin 2009

Translation

During METABOLISM/35.html">Protein Biosynthesis (Translation), the information encoded in the primary Structure of Nucleic Acids is translated into the Amino Acid Sequence of synthesized Polypeptides. A wide variety of Proteins, mRNA, tRNA, rRNA, and other molecules are involved in protein biosynthesis.

Protein Synthesis is characterized by the absence of a complementary match between the template (mRNA) and the product (protein). Consequently, deciphering The nucleotide sequence requires a Genetic Code that establishes a correspondence between the mRNA nucleotide sequence and the polypeptide chain. The unit of The Genetic Code is the codon. A codon is a sequence consisting of three NUCLEOTIDES, i.e., a triplet. There are a total of 64 codons, 61 of which are used to encode the 20 standard Amino Acids. The remaining three codons do not encode Amino Acids and serve as signals for the termination of Polypeptide chain synthesis. These are known as termination or nonsense codons. Each codon, with the exception of the termination codons, corresponds to a strictly specific amino acid. Protein synthesis begins with an initiation codon. Typically, the AUG triplet serves as the initiation codon. Subsequently, each successive codon is decoded in the direction from the 5'-end of the mRNA molecule to the 3'-end. Polypeptide synthesis terminates at one of the three termination codons (Fig. 6.1).

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Fig. 6.1. Scheme of information reading during translation