Translation: Messenger RNA Translated Into ProteinCreated by George Rice, Montana State University Show
Translation is the process that takes the information passed from DNA as messenger RNA and turns it into a series of amino acids bound together with peptide bonds. It is essentially a translation from one code (nucleotide sequence) to another code (amino acid sequence). The ribosome is the site of this action, just as RNA polymerase was the site of mRNA synthesis. The ribosome matches the base sequence on the mRNA in sets of three bases (called codons) to tRNA molecules that have the three complementary bases in their anticodon regions. Again, the base-pairing rule is important in this recognition (A binds to U and C binds to G). The ribosome moves along the mRNA, matching 3 base pairs at a time and adding the amino acids to the polypeptide chain. When the ribosome reaches one of the "stop" codes, the ribosome releases both the polypeptide and the mRNA. This polypeptide will twist into its native conformation and begin to act as a protein in the cells metabolism. (from Biology 101, link
http://edtech.clas.pdx.edu/gene_expression_tutorial/translation.html, John Rueter 11/25/96)
The central dogma of life can be defined in a fairly simple way: DNA makes RNA, which in turn makes proteins: In transcription, your genetic code is transcribed, or written, into RNA. In translation, this RNA is then translated into proteins. Of course, the processes of transcription and translation are a little more complicated than that. Let’s review the two processes: Transcription: DNA → RNATranscription is the first half of the Central Dogma. This is where DNA is translated into RNA. Transcription occurs in the nucleus of the cell—DNA cannot leave the nucleus. There are three steps in transcription: initiation, elongation, and termination (these are also the same steps as in translation; however, different things happen in the steps of the different processes).
RNA PolymeraseThere are three types of eukaryotic RNA Polymerase. Fittingly, they’re named RNA Polymerase I, RNA Polymerase II, and RNA Polymerase III.
mRNA ProcessingAfter transcription, eukaryotic pre-mRNAs must undergo several processing steps before they can be translated. Pre-mRNAs are first coated in RNA-stabilizing proteins; these protect the pre-mRNA from degradation while it is processed and exported out of the nucleus. The three most important steps of pre-mRNA processing are the addition of stabilizing and signaling factors at the 5′ and 3′ ends of the molecule, and the removal of intervening sequences that do not specify the appropriate amino acids. In rare cases, the mRNA transcript can be “edited” after it is transcribed. PRactice QuestionsIn which step of transcription does the DNA unwind? Which is a function of RNA polymerase II?
Translation: RNA → proteinTranslation occurs in the cytoplasm. There are three steps in translation: initiation, elongation, and termination (these are also the same steps as in transcription; however, different things happen in the steps of the different processes).
Ribosomes and tRNAsIn addition to the mRNA template, many molecules and macromolecules contribute to the process of translation.
CodonsThe amino acids that make up proteins are encoded by a nucleotide triplet codon: for example, the protein serine is encoded by the codons UCU, UCC, UCA, and UCG. The reading frame for translation is set by the AUG start codon near the 5′ end of the mRNA. The three “nonsense codons,” UAA, UAG, and UGA indicate that translation should be terminated. Practice QuestionsWhich macromolecule binds to the mRNA template to aid in translation?
What do nucleotide triplet codons encode? What process takes information from DNA and turns it into RNA?During the process of transcription, the information stored in a gene's DNA is passed to a similar molecule called RNA (ribonucleic acid) in the cell nucleus.
How do you go from DNA to RNA to protein?During transcription, the enzyme RNA polymerase (green) uses DNA as a template to produce a pre-mRNA transcript (pink). The pre-mRNA is processed to form a mature mRNA molecule that can be translated to build the protein molecule (polypeptide) encoded by the original gene.
How is RNA turned into proteins in translation?During translation, ribosomal subunits assemble together like a sandwich on the strand of mRNA, where they proceed to attract tRNA molecules tethered to amino acids (circles). A long chain of amino acids emerges as the ribosome decodes the mRNA sequence into a polypeptide, or a new protein.
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