The phosphate group is attached to the 5th carbon thus it is called 5’ whereas the OH group is attached to the third carbon and is known as 3’. And the other strand ends on a hydroxyl group. Organisms propagate the sequence of DNA among generations, therefore, for the continuation of life, the DNA sequence is essential.Īntiparallel Orientation: Both strands of DNA are antiparallel to each other, which means that one strand ends on a phosphate group at the end of a particular molecule. Therefore the genetic information carried out by these nucleotides is also unique in each organism. Genetic Code: All the organisms have a different sequence of nucleotides. Therefore, these strands are called complementary to each other. The guanine and cytosine are connected with three hydrogen bonds whereas adenine and thymine have two hydrogen bonds. For example, adenine always pairs up with thymine, and guanine pairs with cytosine. The DNA strands occur in the outside of the helix, and the nitrogenous bases occur at the core of the helix.Ĭomplementary Base Pairing: The hydrogen bonding between the nucleotides always occurs in a particular manner. Almost always the helix turns in a right-handed direction. The helix turns once every ten nucleotides. Helix Directionality: The DNA molecule is made up of two strands that form a helix by twisting around each other. Watson/Crick model of the DNA double helix has some important features including: He added the name of Rosalind Franklin to the plaque and recognize his important role in the discovery. Thus, they proposed a model that was considered accurate for several decades.Īfter completing the research Crick announced in their local pub in Cambridge that he and Watson had discovered “the secret to life.” To commemorate the occasion, the pub named The Eagle erected a plaque, which was once modified by a member of the public. They carefully construct a series of cardboard models and finally form a structure that made sense. Watson and Crick use all the evidence as well as X-ray crystallography data collected by Rosalind Franklin to derive their model. A lot of research had already been carried out by scientists on the composition of DNA before the publication of the double helix structure.įor example, Chargaff’s rules about the ratio of purines and pyrimidines were already discovered. Wilkins has also an important role in the research thus his biography is also titled, “The Third Man of the Double Helix”. Both the scientists along with Maurice Wilkins were awarded by Nobel Prize for their research. It was first discovered by biologist James Watson and physicist Francis Crick in the 1950s. In the field of biology, the discovery of the structure of DNA is one of the most significant events.
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