The Central Dogma

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The Central Dogma. This hypothesis was described by Crick in 1958. In 1953, Watson and Crick were the first to determine the true crystalline structure of DNA, using model building and then X-ray crystallography. Once the DNA structure was determined, the mechanisms behind inheritance, information flow, and gene function fell into place. Overall the flow of information is depicted as: DNA --> RNA --> protein. Both DNA and RNA can be replicated (i.e. DNA is synthesized from DNA, and RNA from RNA). RNA can be made or transcribed from DNA. It is called transcription since the same type of "language" is used in DNA and RNA -- i.e. nucleic acids. In some cases RNA may be used to make DNA (i.e. "reverse transcription") using a particular enzyme called reverse transcriptase. Protein is synthesized from RNA by translation. It is called translation, because essentially a different "language" is used -- i.e. amino acids (instead of nucleic acids). Once protein has been synthesized from RNA, the information is trapped. In other words, there is no known mechanism that allows information to flow back into RNA from protein. At least, that was what was thought. The recently discovered "prions" indicates that there is in fact a mechanism for a type of protein replication, and this goes against the central dogma. Essentially, the mechanism breaks down as follows. An organism (let's say, a human being), has a "wild type" protein (or a "normal" protein with a specific shape for its proper functioning), which is a homolog to a prion. When the human is infected, the prion interacts with the wild type homolog and causes it to misfold (i.e. the prion causes the wild type protein to change its shape into a prion). Thus, there is a simple mechanism by which certain proteins can replicate. However, this central dogma of information flow is still upheld to some degree. Essentially the central dogma describes the following pathway: DNA makes RNA makes Proteins makes Cell. This suggests...
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