Difference Between DNA and RNA Synthesis

Key Difference – DNA vs RNA Synthesis
 

DNA synthesis is the process of synthesizing a double stranded DNA through semi-conservative replication by using enzymes. RNA synthesis is the process of synthesizing an RNA through the process of transcription using an enzyme-mediated method. The key difference between DNA and RNA synthesis is the type of enzyme used for the process. In DNA synthesis, DNA polymerase is the main enzyme used, whereas, in RNA synthesis, RNA polymerase is used.

CONTENTS

1. Overview and Key Difference
2. What is DNA Synthesis
3. What is RNA Synthesis
4. Similarities Between DNA and RNA Synthesis
5. Side by Side Comparison – DNA vs RNA Synthesis in Tabular Form
6. Summary

What is DNA Synthesis?

DNA synthesis, also known as DNA replication, is the process in which a new double stranded DNA is synthesized by the use of a parent DNA template. DNA replication takes place in the nucleus of eukaryotes. It’s known as the semi-conservative replication method since it produces one copy of original strand and one copy of new strand. DNA replication is governed by an enzyme called DNA polymerase. Replication begins with the unwinding of the double stranded parent DNA with the help of DNA helicase.

DNA polymerase works in the direction of 5’ to 3’ for new strand synthesis. This enzyme requires a 3’OH group to add new nucleotides during replication. And also, DNA polymerase requires a short RNA primer to initiate replication as it cannot initiate replication on its own. The strand which is synthesized in the 5’ to 3’ direction is known as leading strand and it can be synthesized continuously.

Figure 01: DNA Synthesis

The new strand that runs from 3’ to 5’ direction, cannot be synthesized continuously as it does not have a free 3’ end. Therefore, with the aid of many short oligomers (primers), short strands of new DNA are synthesized. These short strands are known as Okazaki fragments. These Okazaki fragments are later ligated using DNA ligase. This strand is known as the lagging strand. At the end of the process, new double stranded DNA similar to the parent DNA is produced.

What is RNA Synthesis?

RNA synthesis is the process in which a single stranded RNA is synthesized with the aid of a double stranded DNA. In the central dogma of life, this is known as transcription. Transcription of eukaryotes takes place in the nucleus. The key enzyme used in transcription or RNA synthesis is RNA polymerase. Transcription also takes place in the 5’ to 3’ direction.

Figure 02: Transcription

RNA polymerase identifies the template strand of the parent DNA by binding to the promoter sites of the DNA strand. Promoter sites differ according to the cellular system of the organism (eukaryotic or prokaryotic). Once the promoter is identified by the RNA polymerase, it begins the transcription at the transcription initiation site. The RNA polymerase adds nucleotides to the free 3’ end and does not require a template to initiate transcription. First the DNA: RNA hybrid is formed which later disappears and upon termination of the RNA synthesis, the synthesized strand is sent to the cell cytoplasm for protein synthesis (translation).

What are the Similarities Between DNA and RNA Synthesis?

• Both DNA and RNA Synthesis are catalyzed by the enzymes.
• Both take place in the nucleus of eukaryotes and cytoplasm of prokaryotes.
• Both are regulated by time and pH conditions.
• Both DNA and RNA Synthesis have three main phases: initiation, elongation, and termination
• Both are two important stages in the Central dogma of life.
• Both occur in 5’ to 3’ direction.

What is the Difference Between DNA and RNA Synthesis?

Summary – DNA vs RNA Synthesis

Replication and Transcription are referred to as the two main processes in which DNA and RNA are synthesized. DNA synthesis or replication takes place by the unwinding of the double strands and both the strands result in producing the daughter double stranded DNA. The process mainly involved DNA polymerase along with other enzymes. RNA synthesis uses one DNA strand to synthesize the RNA using RNA polymerase. Both take place in the 5’ to 3’ direction.

Reference:

1.Griffiths, Anthony JF. “Mechanism of DNA Replication.” An Introduction to Genetic Analysis. 7th Edition., U.S. National Library of Medicine, 1 Jan. 1970. Available here 
2.Alberts, Bruce. “From DNA to RNA.” Molecular Biology of the Cell. 4th Edition., U.S. National Library of Medicine, 1 Jan. 1970. Available here  

Image Courtesy:

1.’0323 DNA Replication’By OpenStax, (CC BY 4.0) via Commons Wikimedia 
2.’Process of transcription (13080846733)’By Genomics Education Programme, (CC BY 2.0) via Commons Wikimedia

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