Elongation

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Elongation: It requires Initiation complex, aminoacyl tRNAs, GTP and EF(elongation factors such as EF-TU, EFTs, EF-G) Now incoming aminoacyl tRNA bind to GTP bound EF-TU complex and this complex bind to A site. Eukaryotes do not have E site, tRNA removed directly from P site. Second aminoacid along with EF-Tu enters ribosome and bind to A site and amino acid 1 remains at P site, another next aminoacid binds to A site by shifting second to P site this way elongating the aminoacid chain. tRNA moves out from E site leaving aminoacid on chain. Each coming aminoacid requires peptidyl transferase enzyme for chain elongation. Peptidyl transferase step is energy independent and requires ribozyme. A peptide bond is formed between two amino acids by their tRNAs. Termination: 1. Takes place when ribosome encounters stop codon UAA,UAG,UGA. RFs are releasing factors, RF1 recognise UAA,UAG. RF2 recognise UAA and UGA. RF release the peptide, ribosome, mRNA, tRNA and the complex diassembles. some mutations: Missense mutation: cause aminoacid change. Nonsense mutation: change aminoacid to stop codon,cause termination of peptide. Silent Mutation: without apparent affect. Synonymous mutation: same aminoacid as parent, nucleotide change do not change amino acid. Neutral mutation: functionally equivalent aminoacid is replaced, not much effect. Free life science studymaterial.