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The process of creating a protein from the information given from DNA consists of two parts: transcription and translation.
The first process transcription is copying the information from DNA to mRNA. The process starts when DNA double helix opens and in one strand a RNA polymerase attaches and starts to bind free nucleotides to DNA, so G bonds with C and A with U (because RNA does not have T). When this RNA polymerase reaches a part of DNA called the terminator, the transcription process stops and mRNA leaves the nucleus. A sequence of three bases code for one aminoacid. In mRNA this is called a codon.
The second process translation does the “translation” from the language of bases to the language of aminoacids which make up proteins. After mRNA leaves the nucleus it travels to ribosomes, a cell part where proteins are made. In ribosomes, another type of RNA, the tRNA is used as a “translator” between mRNA and aminoacid. In one end of tRNA there is a “anticodon” which is complementary to the codon of mRNA. (example if the codon in mRNA says AGG, the anticodon of tRNA will be UCC). This was the tRNA knows in which specific mRNA to attach to. In the other end of tRNA there is a site where the specific aminoacid is attached. Ribosomes have several sites. The P site holds the growing polypeptide chain, the A site holds the next aminoacid that comes, and the E site is the exit site where the polypeptide chain detaches. A particular tRNA called initiator tRNA comes in and bonds with the mRNA on the P site. This tRNA always carries a particular amino acid – always methionine (MET) which is the “Start” aminoacid. A new tRNA with its amino acid comes in to the ribosome and bonds to the A site. The first tRNA on the P site leave, and the new tRNA with the two amino acids now moves to the P site. This process continues until the whole polypeptide is made. The process stops where mRNA codes for a tRNA that never carries an amino acid. This is called a stop codon. This way the process stops and the newly made polypeptide chain leaves the ribosome.
Mohaissack answered the question on October 4, 2017 at 08:50
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