Watson and crick model of DNA Assignment Help
DNA; deoxyribose nucleic acid, that is one of the most important molecules of life.
Before Watson and crick, many scientists worked on the model of DNA, to find out the reason for transfer of hereditary information. In this race, Miescher was the first one. In one of his experiment he discovered a substance from a pus coated bandied of a patient that had chemical properties different from that of protein. The content of phosphorous was much more than expected along with the activity of proteolysis. Therefore, this made him realize that the substance he is looking on is completely new and need further research. But again, this research was further carried by Levene and he proposed tetra nucleotide structure of the DNA. Again, this was not the end; Chargaff was another scientist who came after Leven and carried the research further. After his experiment he made two major conclusions, among them one states that nucleotide sequence in DNA is different in different species and second that some of the basic properties of DNA are same in the entire organism. he also gave a mathematical formulation that the amount of adenine is similar to that of thymanine and on the other hand the amount of guanine is similar to that of cytosine which gives: A+G= T+C. This rule is also known as Chargaff rule that is given after his name.
After him were Watson and crick, who already have raw materials for their further study. They already have some information regarding DNA and its structure, so they carried on the further researches to give us the final and correct structure of DNA molecule.
Watson and crick is the two scientists who studied in the structure of DNA. These scientists were successful in their task and hence were awarded with Nobel Prize in 1962.
Image reference: www.g10biodna-a.wikispaces.com
DNA is the central molecule that contains hereditary information and Watson and crick in 1953 proved this along with the structure of the DNA. They explained several features of DNA molecule. Firstly, this is a double stranded molecule with two DNA strand linked in anti- parallel manner. These strands are made up of repeating units called nucleotides. The pitch of each axis of DNA is 3.4 nanometer and radius is 10 angstrome. Beside this, one unit of nucleotide was found out to be 3.3 angstrom. One end of the strand is 5 and the other end is 3, thus one strand runs from 5 to 3 direction and the other is from 3 to 5 direction. These strands are tangled around each other and are bond due to opposite pairing of the nitrogenous bases. The bases involved are from two groups; purines and pyrimidines. One hand purines pairs only with pyrimidines and same is the case with the pyrimidines that pairs only with purines. Here purines are adenine and guanine and pyrimidines are thymine and cytosine. Therefore, A that is adenine pair with thymine whereas guanine pair with cytosine. These pairing are well facilitated by the establishment of hydrogen bond between these bases. The number of bonds involved is also different, i.e. the bond between guanine and cytosine is three and that of adenine and thymine is only two. Beside the connection and pairing of bases, many more things are present in DNA molecule. The remaining molecule is sugar- phosphate backbone, where the sugar is 2- deoxyribose. All these together support the two strand of DNA to remain connected and in proper structure. Though presently different forms have DNA have been studied but earlier B form was described by Watson and crick. Replication, transcription and translation are several mechanism that takes place in further steps and this scientist have been able to trace out every small information on this only after the identification of structure of DNA.
Though Watson and Crick was the first person to initiate the finding on hereditary molecule, but they started this research with available information and completed it with further researches and is the reason that we name it as Watson and crick model of DNA. The research didnt end here; further researches were carried on to know about involvement and importance of DNA in an individual life.
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