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Translations (Initiation in Eukaryotes (Elongation, Elongation is fairly…
Translations
Initiation in Eukaryotes
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The next tRNA binds to the codon, bringing the appropriate amino acid to the ribosome, and a peptide bond joins between the start methionine and the next amino acid. This reaction is catalyzed by the ribosome.
The first tRNA now leaves the ribosome. The A site accepts a tRNA with an attached amino acid, a peptide bond forms between the two adjacent amino acids, and the process continues.
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Translation
translation is “RNA → protein.” In other words, translation is the transfer of the genetic instructions in RNA to a protein made of amino acids.
The mRNA moves from the nucleus to the cytoplasm to interact with a ribosome, which serves as the site of translation. Translation proceeds in three phases: initiation, elongation and termination.
Prokaryotic subunits are named the 30S and 50S subunits; eukaryotic subunits are named the 40S and 60S subunits. During translation the tRNA molecules are literally “inside” the ribosomal subunits, as they sit on the mRNA strand.
The A site binds a tRNA with an attached amino acid. The P site contains the tRNA with the growing polypeptide chain attached, and the E site contains the tRNA that no longer has an attached amino acid. This tRNA is preparing to exit the ribosome. A single mRNA can be translated simultaneously by multiple ribosomes.
Role of tRNA
Transfer RNAs or tRNAs bring or tansfer the proper amino acid to the ribosome based on the genetic code. The anticodon at the bottom of the tRNA molecule binds to the codon on the mRNA.
Transfer RNAs or tRNAs bring or tansfer the proper amino acid to the ribosome based on the genetic code. The anticodon at the bottom of the tRNA molecule binds to the codon on the mRNA. The codon on the mRNA is specific for an amino acid or stop codon. Stop codons do not have corresponding tRNA molecules, and signify the end of translation.
The covalent attachment of an amino acid to the tRNA is catalyzed by enzymes called aminoacyl-tRNA syntheses through a process called aminoacylation.
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Termination
Termination of translation occurs when the ribosome comes to one of the three stop codons, for which there is no tRNA. At this point, a protein called a release factor binds to the A site.
The release factor causes the addition of a water molecule to the polypeptide chain, resulting in the release of the completed chain from the tRNA and ribosome.