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Transcription is simple to understand as a means of information transfer: since DNA and RNA are chemically and structurally similar, the DNA can act as a direct template for the synthesis of RNA by complementary base-pairing.Genetic code In contrast, the conversion of the information in RNA into protein represents a translation of the information into another language that uses quite different symbols. ![]() ![]() In eucaryotic cells, the process of transcription is much more complex, and there are three RNA polymerases polymerase I, II, and III-that are related evolutionarily to one another and to the bacterial polymerase.FROM RNA TO PROTEIN An mRNA Sequence Is Decoded in Sets of Three Nucleotides Once an mRNA has been produced by transcription and processing, the information present in its nucleotide sequence is used to synthesize a protein. An mRNA molecule is produced when this enzyme initiates transcription at a promoter, synthesizes the RNA by chain elongation, stops transcription at a terminator, and releases both the DNA template and the completed mRNA molecule. Bacteria contain a single type of RNA polymerase (the enzyme that carries out the transcription of DNA into RNA). This allows the amount of protein A in the cell to be much greater than that of protein B.Portions of DNA Sequence Are Transcribed into RNA (transcription.)The first step a cell takes in reading out a needed part of its genetic instructions is to copy a particular portion of its DNA nucleotide sequence-a gene-into an RNA nucleotide sequence.īases in other configurations are indicated by broken rungs.Review: TranscriptionBefore the synthesis of a particular protein can begin, the corresponding mRNA molecule must be produced by transcription. In this example, gene A is transcribed and translated much more efficiently than gene B. But each gene can also be transcribed and translated with a different efficiency, allowing the cell to make vast quantities of some proteins and tiny quantities of othersHow Cells Read the Genome: From DNA to ProteinGenes can be expressed with different efficiencies. Because many identical RNA copies can be made from the same gene, and each RNA molecule can direct the synthesis of many identical protein molecules, cells can synthesize a large amount of protein rapidly when necessary. The flow of genetic information from DNA to RNA (transcription) and from RNA to protein (translation) occurs in all living cells Transcription and translation are the means by which cells read out, or express, the genetic instructions in their genes. This primer is erased by a special DNA repair enzyme (an RNAse H) that recognizes an RNA strand in an RNA/DNA helix and fragments it this leaves gaps that are filled in by DNA polymerase and DNA liqaseFROM DNA TO RNA The pathway from DNA to protein. ![]() In eucaryotes, RNA primers are made at intervals spaced by about 200 nucleotides on the lagging strand, and each RNA primer is approximately 10 nucleotides long. On the lagging strand, the Okazaki fragments are synthesized sequentially, with those nearest the fork being the most recently made.The synthesis of one of many DNA fragments on the lagging strandThe synthesis of one of many DNA fragments on the lagging strand. #Materi yang berkaitan dengan sintesis asam amino seriesBecause both daughter DNA strands are polymerized in the 5’ to 3'direction, the DNA synthesized on the lagging strand must be made initially as a series of short DNA molecules, called Okazaki fragments. The original strands therefore remain intact through many cell generationsThe structure of a DNA replication forkThe structure of a DNA replication fork. In a round of replication, each of the two strands of DNA is used as a template for the formation of a complementary DNA strand. ![]()
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