Sunday, 2 July 2017

DOUBLE HELICAL STRUCTURE OF DNA(WASTON AND CRICK'S MODEL)

By Unknown July 02, 2017 1 comment
Learning informally of franklin's result,before they were published in 1953, James waston and Francis Crick, two researchers in the university of Cambridg,quickly worked out likely structure of the DNA molecule which we now know was substantially correct.They They proposed that molecule is a single double helix,with the basis of two starnds pointed inward toward each other, theu forming base pairs.In their model base pairs always consist of purines,which are large, pointing toward pyrimidyens which are small, keeping the diameter 2 nm .Because hydrogen bond exist between the bases in the base pairs.The double helix is stabilized as a double DNA molecule composed of two antiparallel strands one chain running 5' to 3'.The base pairs are planer and stack 0.34nm apart as a result of hyperphobic interactions contributing to the overall stability of the molecule. In the double helix adenine forms two hydrogen bonds with thymine,while guanine form three hydrogen bonds with cytosine.Adenine will not form proper hydrogen bond s with cytosine.
X ray diffraction patterns suggested the double helical shape of DNA.
Consequently adenine and thymine will always occurs in the same proportion in any DNA molecule, as well guanine and cytosine,because of this base pairing.
DNA REPLICATION:   The Waston Crick model immediately suggested that the bases for copying the genetic information is complementary.If one where to unzip the molecule one would need only to assemble the the appropriate coplementry nucleotides on the exposed single strands to form two daughter complexes with the same sequence.This form of DNA replication is called semi conservation because while the sequence of the original duplex is conserved after one round of replication,the duplex itself is not.Instead each strand of duplex become the part of another duplex. In semi conservation repkicarion, two strands of duplex seperate out each acting as a model or mold,along which newcnucleotides are arranged thus giving rise to two new duplex.In this process by separation of two strands ,primary structure has been conserved, whereas the secondary structure has been disrupted.
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1 comment:

  1. karthika12 April 2023 at 04:39

    The article provides a clear explanation of the double helical structure of DNA proposed by Watson and Crick. It also highlights the significance of base pairing in maintaining the stability of the molecule and how it facilitates DNA replication. The use of simple language and concise explanations makes it easy to understand for readers with basic knowledge of biology. However, it would have been helpful if the article had provided more information on Rosalind Franklin's contribution to the discovery of the double helix structure, as her work was crucial in providing the X-ray diffraction images that supported Watson and Crick's model. Overall, it's a well-written article that provides a good introduction to the fundamental concepts of DNA structure and replication. Please to discuss more about Top 5 Neet Coaching Centres in Chennai

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