posted 04-14-2015 02:14 AM            

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Replication stands for duplication and DNA replication is process by which an identical copy of DNA is produced using the existing DNA template through DNA synthesis, a new DNA strand is formed. In humans the replication takes place with the cell nucleus.
However, the DNA replication was not introduced before 1953 when Watson and Crick proposed to define the molecular structure of DNA. It was a landmark discovery in biology. But, it wasn’t accepted as scientists have their doubts on Watson and Crick’s findings. They believed that the model was not right. They didn’t only propose the structural model of the DNA but also described how DNA is replicated within the cell. It didn’t go well with many scientists as they thought it doesn’t make sense, and many concerned scientists even doubted the presence of double helix. The problem was later solved but it will be interesting to see how.
Before Watson and Crick a lot of scientists were aware of the fact that organisms make duplicate copies of their DNA. Making extra copies of DNA allows the organism to reproduce and grow. Here the copy denotes the replication of the DNA.
It is important to know and understand the DNA before we can actually understand the whole process of DNA replication. The DNA chain consists of smaller components which are known as nucleotides. The nucleotides are a composition of sugar, phosphate and have a nitrogenous base. Nucleotides are arranged in two strands like stairs on a ladder and here the ladder is twisted into a different kind of shape which is called double helix. Watson and Crick in their observation and discovery offered the same model which was later acknowledged after scientists found their proposal accurate. But, the question is why they were challenged by the scientists at first before accepting the same?
Models for DNA Replication
In DNA replication proposal Watson and Crick suggested that for a DNA to copy itself, it would have to open down the center, similar to the zipper, which would help the new DNA strand to build on top of the visible strands. Following the rules of base pairing; adenine with thymine and cytosine with guanine can be paired. Since the DNA strand serves as a template for the new DNA, this model was called template model.
Watson and Crick coined the term semi-conservative model for the DNA replication because here the model would give two new double strands of DNA, each have one strand of parent DNA and one of daughter, the newly synthesized, DNA.
When scientists couldn’t understand Watson and Crick model of DNA Replication as double helix possibly, in their eyes, cannot open itself without getting tangled or torn apart. Then they came up with dispersive model of DNA replication in which they suggested that DNA copies itself only for short period of time, produces a new strand that is a varied parent and daughter DNA.
After semi-conservative and Dispersive model another model called Conservative model of DNA replication was presented until 1958 when Matthew Meselson and Franklin Stahl tested all three models at once and found that one parental DNA strand can actually generate a series of copies.

For more information visit on- http://www.biosyn.com/dna-synthesis.aspx

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As a pioneer in oligonucleotide synthesis, Bio-Synthesis has been pursuing the development of new oligonucleotide-based techniques that can produce compounds with superior binding affinity and chemical/biological stability. As such, Bio-Synthesis has introduced a third generation of nucleic acid analogs, Bridged Nucleic Acid (BNA).  These are RNA analogues which can be synthesized and spiked with DNA or RNA in order to modify the formation of nucleic acid helices. 

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