DNA replication

Published on October 1, 2007 Reviewed on January 19, 2016   25 min

Other Talks in the Category: Genetics & Epigenetics

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DNA replication.
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DNA is the genetic material of the cell that carries all the information for cell survival and its replication. So every time a cell divides, the DNA needs to be duplicated. During mitosis or meiosis, a parental cell is divided into two daughter cells. And during this process, the DNA is efficiently and faithfully replicated.
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The chemical composition of the DNA was known for some time. DNA is a polymer, and it is made of repeating units of phosphate, sugar, and bases. These units are arranged to give the DNA polymer a polarity or directionality. So the DNA chain has a three prime end and a five prime end. The DNA chain also has four kinds of bases, two pyrimidines, cytosine, and thymine, and two purines, adenine and guanine.
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Chargaff studied the base composition of many genomes, and the observation was made that there were equal number of A's and T's, adenine and thymines, in the genome, as well as equal number of G's and C's in the genome. This is known as the Chargaff's rule. What remained a mystery, though, was how the DNA chain that we just saw in the previous slide was duplicated, or replicated, during each cell division.
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The mystery was solved when the work of four scientists led to the discovery of the DNA structure. In a seminal paper published in 1953 in the journal Nature, Watson and Crick, using the data of x-ray crystallography, proposed a structure of the DNA, n and this structure was a double helix.