DNA replication

Published on October 1, 2007 Reviewed on April 27, 2022   25 min

A selection of talks on Cell Biology

DNA Replication.
DNA is the genetic material of the cell that carries all the information for cell survival and its propagation. Every time a cell divides the DNA needs to be duplicated. During mitosis and meiosis, a parental cell is divided into two daughter cells. During this process, the DNA is efficiently and faithfully replicated.
The chemical composition of DNA has been 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 a directionality. The DNA chain has a 3' end and a 5' end. The DNA chain also has four kinds of bases. Two pyrimidines, cytosine and thymine, and two purines, adenine and guanine.
Chargaff studied the base composition of many genomes, and an observation was made that were an equal number of As and Ts, adenines and thymines, in the genome, as well as an equal number of Gs and Cs in the genome. This is known as the Chargaff's Rule. What remained a mystery was how the DNA chain, that we just saw in the previous slide, was duplicated or replicated during each cell division.
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 Nature journal, Watson and Crick, using the data from X-ray crystallography, proposed a structure of the DNA. This structure was a double helix.