with sample essay by Ala’a Ahmed Salem Abughefreh
Introduction 1. State the process and why it is important. 2. Provide general background information on the process. 3. Define the process. 4. State the thesis. |
Body 1. Using time order, describe what happens during each step in the process. 2. If there are a lot of steps, group them into several main categories. |
Conclusion 1. Paraphrase the thesis. 2. Summarize the main steps in the process. 3. Review why the process is important. |
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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 of DNA replication process necessary for genetic inheritance and
existence, namely, unwinding, complementary base pairing and joining. The first stage of the process is the unwinding of old strands
of the parent DNA molecule. The two strands of the double helix are first
separated by enzymes. Then, each strand acts as a template for the synthesis
of a new complementary DNA molecule. Proteins play a major role in this
stage. The stability of the |
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The
Process of DNA Replication 2 replication fork is maintained by the
single-stranded binding proteins. 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. |
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The
Process of DNA Replication 3 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 together, forming the side
rail of the new DNA molecule. In addition, the final replication product has
no nicks because of the action of DNA ligase. In conclusion, DNA replication is a
three-stage process. Unwinding, complementary base pairing and joining form
the basis of the process of DNA replication. This process is crucial for
ensuring continuous transmission of the genetic information through
generations. |