 This is addressed by the ribosome not activating the GTPase activity of EF-Tu if the tRNA in the ribosome's A-site does not match the mRNA codon, thus preferentially increasing the likelihood for the incorrect tRNA to leave the ribosome.Additionally, regardless of tRNA matching, EF-Tu also induces a delay after freeing itself from the aa-tRNA, before the aa-tRNA fully enters the A-site (a process called accommodation).This delay period is a second opportunity for incorrectly charged aa-tRNAs to move out of the A-site before the incorrect amino acid is irreversibly added to the polypeptide chain.