Dna Replication Essay Example

Dna Replication Essay examples

2166 Words9 Pages



DNA is a molecule that has a repeating chain of identical five-carbon sugars (polymers) linked together from head to tail. It is composed of four ring shaped organic bases (nucleotides) which are Adenine (A), Guanine (G), Cytosine (C) and Thymine (T). It has a double helix shape and contains the sugar component deoxyribose.


How DNA replicates is quite a simple process. First, a DNA molecule is “unzipped”. In other words, it splits into two strands of DNA at one end of the DNA molecule. This separation will cause a formation of a replication fork.
After the replication fork has been established the strands of DNA are ready for the next stage. On each strand is a sequence…show more content…

 The first discovery Chagraff made was that the amount of adenine present in all DNA molecules is equal to the amount of thymine.
 The second discovery Chagraff made was that the amount of guanine was equal to the amount of cytosine.
 The third discovery Chagraff made was that the amount of adenine plus thymine often differs greatly from the amount of guanine plus cytosine.


After Chagraff’s discoveries, two British scientists by the name Rosalind Franklin and Maurice Wilkens were able to apply his observations. Thus, these two scientists were the first ones to discover the image of what a DNA molecule actually looked like in three-dimension.
     How these scientists manage to obtain the image of a DNA molecule was by the use of “x-ray crystallographic analysis”. In this process, DNA molecules are bombarded with a x-ray beam. These x-rays encounter atoms, which in turn causes their paths to bent or diffract. The pattern created by the sum of total of these diffractions are then captured on a photographic film. The pattern is then interpreted into the image of the molecule through careful analysis. Thus, because of this research it led to the first theory and model structure of DNA.

Maurice Wilkens was born in the year 1916 and is a British

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The Process of DNA Replication Essay

487 Words2 Pages

The Process of DNA Replication


The process of DNA replication plays a crucial role in providing genetic continuity from one generation to the next. Knowledge of the structure of DNA began with the discovery of nucleic acids in 1869. In 1952, an accurate model of the DNA molecule was presented, thanks to the work of Rosalind Franklin, James Watson, and Francis Crick. To reproduce, a cell must copy and transmit its genetic information (DNA) to all of its progeny. To do so, DNA replicates following the process of semi-conservative replication. Two strands of DNA are obtained from one, having produced two daughter molecules that are identical to one another and to the parent molecule. This essay reviews the three stages…show more content…

Moreover, there are many enzymes that participate in the unwinding of the old strands of DNA molecule such as topoisomerase. This enzyme is responsible for initiation of the unwinding of the old strands of DNA molecule. Once supercoiling has been eliminated by the topoisomerase, helicase accomplishes unwinding of the original double strand. In order to aid with the unwinding process, DNA gyrase catalyzes the formation of negative supercoils. The unwound helix, with each strand being synthesized into a new double helix, is called the replication fork.


The second stage of the process is complementary base pairing. In this stage, new complementary nucleotides are positioned following the rules of complementary base pairing: adenine (A) to thymine (T) and guanine (G) to cytosine (C). Then, the binding of free nucleotide with complementary bases is catalyzed by DNA polymerase.


The last stage of the process, joining, involves bonding of complementary nucleotide to each other so as to form new strands. The nucleotides are joined to one another by hydrogen bonds to form a new DNA molecule. This joining continues until a new polynucleotide chain has been formed alongside the old one, forming a new double-helix molecule. This stage of the process also takes place with the assistance of enzymes. The DNA polymerase links the complementary nucleotides

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