Fundamentals of Molecular Biology. Part 2: Molecular Genetic Mechanisms - A. N. Ogurtsov 2011

The Role of RNA in Translation
Three Functions of RNA in Translation

Although DNA stores the blueprint for Protein Synthesis AND mRNA carries the instructions for Biosynthesis, the vast majority of biological Functions are performed by Proteins. The linear sequence of Amino Acids in each protein molecule dictates its three-dimensional Structure and activity. Therefore, the precise folding of amino acids in the exact order encoded by DNA is a critical process for the synthesis of functional proteins, and consequently for the proper functioning of Cells and organisms.

Translation is the comprehensive process by which The nucleotide sequence of mRNA is used to link amino acids into a polypeptide protein molecule.

In Eukaryotic cells, protein synthesis takes place in the Cytoplasm, where Three types of RNA molecules collectively perform distinct yet complementary, cooperative functions (Figure 32).

Class="center">

Figure 32 - Three functions of RNA in translation, aa — designation for amino acids; R - designation for amino acid residues

1. Messenger RNA (mRNA) carries the Genetic information transcribed from DNA AS A set of codons—three-nucleotide sequences, each of which specifies a particular amino acid.

2. Transfer RNA (tRNA) acts as a key in decoding mRNA codons. Each type of amino acid has its own specific set of tRNAs to which these amino acids attach, delivering them to the growing end of the polypeptide chain whenever the next codon in the mRNA "calls for" their arrival.

At each step of METABOLISM/35.html">Protein Biosynthesis, a new mRNA codon selects the appropriate tRNA with its attached amino acid, owing to the fact that each tRNA possesses an anticodon—a three-nucleotide sequence capable of base-pairing with the complementary NUCLEOTIDES of the mRNA codon.

3. Ribosomal RNAs (rRNAs) associate with sets of specific proteins to form Ribosomes—complex Organelles that (1) physically move along the mRNA molecule while (2) catalyzing the assembly of amino acids into a polypeptide chain. They also (3) recruit (in the correct sequence and at the appropriate time) tRNA molecules and various accessory proteins required for protein synthesis.

Ribosomes consist of large and small subunits, each containing its own characteristic rRNAs.

These three types of RNA participate in translation across all cells.