THE CENTRAL DOGMA OF MOLECULAR BIOLOGY
Translation
Initiation
The small ribosomal subunit binds to the mRNA at the AUG start codon. The leader sequences upstream of the AUG sequence helps the ribosome identify the AUG sequence. The initiator tRNA binds to the start codon, and one of the initiation factors is released. When the large ribosomal subunit binds to the small subunit and the remaining initiation factors are released, the initiation complex in complete.
Elongation
The polypeptide chain is covalently bonded to the tRNA that carries the amino acid most recently added to the chain. This tRNA is in the P site of the ribosome. An aminoacyl-tRNA binds to the A site by complementary base pairing between the tRNA's anticodon and the mRNA's codon.
The growing polypeptide chain detaches from the tRNA molecule in the P site and become attached by a peptide bond to the amino acid linked to the tRNA at the A site. In the translocation step, the ribosome moves one codon toward the 3' end of mRNA. As a result, the growing polypeptide chain is transferred to the P site. The uncharged tRNA in the E site exits the ribosome.
Termination
When the ribosome reaches a stop codon, the A site binds to a protein release factor. The release factor hydrolyses the bond between the polypeptide chain and the tRNA, causing the release of the polypeptide chain from the tRNA molecule in the P site. The remaining parts of the translation complex dissociate.
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The process by which the base sequence directs the amino acid sequence is called translation. 3 steps involved in translation are initiation, elongation and termination.