ng enzymes in the cytoplasm. Even after the cap and tail are placed onto the mRNA it is not yet ready, it needs the introns cut out. Introns are the useless sections of the DNA. After they are cut out what is left is a shorter, more mature mRNA. Then it heads off to the ribosome where the mRNA binds to the small ribosomal unit, then the initiation codon (AUG) pairs with the tRNA. This becomes the first amino acid in the peptide chain. Now the large ribosomal subunit binds to the small, which completes the complex.The P and A sites are the two places where translation takes place in a ribosome. At this time the initiation codon is at the P site and the codon for the second amino acids at the A. A tRNA with a complimentary anticodon binds to the second mRNA codon, at the A site. The amino acid carried by the tRNA will become the second amino acid in the chain. Then an enzyme joins the two amino acids together by a peptide bond. Then the AUG leaves and empties the P site which is taken up by the second codon and the A site is filled with the third codon. This is called translocation. When the beginning of the mRNA comes out of the ribosome another can be there to start transcribing it. These steps repeat until they hit a termination codon. After this, the peptide chain is not yet a protein. Most of the time the first methonine must be removed and also some of its neighbors. Chemical groups can also be changed around, while sulfur bridges must be formed between parts of the molecule or even two separate chains to make up the larger protein....
