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It can be stated in a very short and oversimplified manner as "DNA makes RNA makes proteins, which in turn facilitate the previous two steps as well as the replication of DNA", or simply "DNA->DNA->RNA->protein". This process is therefore broken down into three steps: transcription, translation, and replication. By new knowledge of the RNA processing, a fourth step must be included: splicing.
In eukaryote cells the primary transcript (pre-mRNA) is processed. One or more sequences ( intronIntrons are sections of DNA within a gene that do not encode part of the protein that the gene produces, and are spliced out of the mRNA that is transcribed from the gene before it is exported from the cell nucleus. Introns exist mainly (but not only) ins) are cut out. The mechanism of alternative splicingAlternative splicing is the process that occurs in eukaryotes in which the splicing process of a pre-mRNA can lead to different ripe mRNA molecules and therefore to different proteins. Also viruses have adapted to this biochemical process when using the p makes it possible to produce different mature mRNA molecules, depending on what sequences are treated as introns and what remain as exonIn some organisms exons are situated between introns which are spliced from the strand before it is exported from the nucleus and do not code for protein parts. Exons are the regions of a transcribed gene that are not spliced out and which are retained ins.
Eventually, this mature mRNA finds its way to a ribosomeA ribosome is an organelle composed of rRNA (synthesized in the nucleolus) and ribosomal proteins. It translates mRNA into a polypeptide chain (e. a protein). It can be thought of as a factory that builds a protein from a set of genetic instructions., where it is translated. In prokaryotic cells, which have no nuclear compartment, the process of transcription and translation may be linked together. In eukaryotic cells, the site of transcription (the nucleusIn chemistry and physics, the nucleus atomic nucleus is the collection of protons and neutrons in the center of an atom that carries the bulk of the atom's mass and positive charge. In cell biology, the nucleus cell nucleus is the membrane-bound subcellul) is usually separated from the site of translation (the cytoplasm), so the mRNA must be transported out of the nucleus into the cytoplasm, where it can be bound by ribosomes. The mRNA is read by the ribosome as triplate codons, usually beginning with an AUG, or initiator methonine codon downstream of the ribosome binding site. Complexes of initiation factor s and elongation factor s bring amino acylated transfer RNAs (tRNAs) into the ribosome-mRNA complex, matching the codon in the mRNA to the anti-codon in the tRNA, thereby adding the correct amino acid in the sequence encoding the gene. As the amino acids are linked into the growing peptide chain, they begin folding into the correct conformation. This folding continues until the nascent polypeptide chains are released from the ribosome as a mature protein. In some cases the new polypepeptide chain requires addtional processing to make a mature protein. The correct folding process is quite complex and may require other proteins, called chaperone protein s. Occasionally proteins themselves can be further spliced, when this happens the inside "discarded" section is known as an intein.