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The anticodon of an incoming aminoacyl tRNA base-pairs with the complementary mRNA codon in the A site. MRNA Ribosome ready for next aminoacyl tRNAġ Codon recognition. In the elongation stage of translation – Amino acids are added one by one to the preceding amino acid TRANSCRIPTION.The initiator tRNA is in the P site the A site is available to the tRNA bearing the next amino acid. GTP provides the energy for the assembly. Proteins called initiation factors (not shown) are required to bring all the translation components together. This tRNA carries the amino acid methionine (Met).Ģ The arrival of a large ribosomal subunit completes the initiation complex. An initiator tRNA, with the anticodon UAC, base-pairs with the start codon, AUG. In a prokaryotic cell, the mRNA binding site on this subunit recognizes a specific nucleotide sequence on the mRNA just upstream of the start codon. The initiation stage of translation – Brings together mRNA, tRNA bearing the first amino acid of the polypeptide, and two subunits of a ribosome P siteĪ small ribosomal subunit binds to a molecule of mRNA.Ribosome Association and Initiation of Translation (The asterisks mark bases that have been Figure 17.14a chemically modified, a characteristic of tRNA.) The anticodon triplet is Anticodon unique to each tRNA type. The four base-paired regions and three U * A G loops are characteristic of all tRNAs, as is the base sequence of the A amino acid attachment site at the 3 end. A tRNA molecule – Consists of a single RNA strand that is only about 80 nucleotides long 3 A Amino acid – Is roughly L-shaped C attachment siteĬ A 5 C G G C C G U G U A A U A U U C UA A G * C A C AG * G * CUC * G U G U * G C C G A G A G G * * U C * G A * G C Hydrogen G C U A bonds G * A * A C Two-dimensional structure.TRNA with amino acid Ribosome attached Gly tRNA Anticodon A A A U G G U U U G G C RNA splicing Is carried out by spliceosomes in some cases Mekanisme post-transkripsi RNA transcript (pre-mRNA) Introns cut out and exons spliced together Eventually, the RNA transcript is released, and the polymerase detaches from the DNA.įase Inisiasi Transkripsi 1 Eukaryotic promotersĪ modified guanine nucleotide added to the 5 end TRANSCRIPTIONĥ0 to 250 adenine nucleotides added to the 3 end In the wake of transcription, the DNA strands re-form a double helix.

The polymerase moves downstream, unwinding the DNA and elongating the RNA transcript 5  3 . Template strand of DNA transcript 2 Elongation. After RNA polymerase binds to the promoter, the DNA strands unwind, and the polymerase initiates RNA synthesis at the start point on the template strand. (When completed, the polypeptide is released from the ribosome.)ĭNA Initiation.

mRNAĪMINO ACID ACTIVATION 4 Each amino acid attaches to its proper tRNA with the help of a specific enzyme and ATP.Ī succession of tRNAs add their amino acids to Anticodon the polypeptide chain as the mRNA is moved through the ribosome one codon at a time. RNA transcript (pre-mRNA) Intron Aminoacyl-tRNA synthetase NUCLEUS Amino acid tRNAĬYTOPLASM 3 After leaving the nucleus, mRNA attaches to the ribosome. RNA transcript (premRNA) is spliced and modified to produce mRNA, which moves from the nucleus to the cytoplasm. Pada molekul RNA, T diganti oleh U.Įkspresi Gen pada Eukariotik dan Prokariotik Molekul RNA merupakan antiparalel terhadap template DNA strand atau paralel terhadap coding DNA strand. Ketiga kodon tersebut juga disebut kodon nonsense, karena tidak mengkode satu asam amino pun.