Descriptive Process Essay

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.