Difference Between Conservative and Semiconservative Replication

The key difference between conservative and semiconservative replication is that the conservative replication produces two double helices in which one helix contains entirely old parental DNA and the other helix contains entirely new DNA while semiconservative replication produces double helices in which each strand of the two double helices formed would have one old and one new strand.

DNA exists as a double helix comprised of two complementary strands. DNA synthesis or DNA replication is the process of producing replicas of DNA from original DNA molecules. Therefore, it is an extremely important process, as it facilitates the passing of genetic material from parent to offspring. In other words, DNA replication is the basis of heredity or the biological inheritance. There are three postulated methods of DNA replication; namely, semiconservative replication, conservative replication and dispersive replication. Among these three, conservative and dispersive replication is not found to be biologically significant.

CONTENTS

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

What is Conservative Replication?

Conservative replication is one of the three methods of DNA replication. During this process, it produces two DNA helices from one original DNA helix. Out of two helices formed, one helix contains entirely old DNA while the other helix contains an entirely new DNA.

Figure 01: Conservative Replication

Moreover, this mode of replication is not found to be biologically significant. In this model of replications, scientists believed that DNA does not split open at all. Therefore, they argued that somehow keeping parent strands intact, entirely new and separate copy of DNA forms in this model.

What is Semiconservative Replication?

Semiconservative replication is the biologically significant mode of DNA replication that is proposed by Watson and Crick in 1953. In this method, out of two helices formed, each helix contains one new strand and one old strand. According to Watson and Crick, during semiconservative replication, one old DNA strand serves as a template to form the new strand.

Figure 02: Semiconservative Replication

Hence, each new double helix produced contains one old DNA strand every time. However, this mode of DNA replication is reasonable than the other two modes, as DNA polymerase enzyme needs a template strand to form a new strand and there is a possibility of combining a new strand with the template strand during replication.

What are the Similarities Between Conservative and Semiconservative Replication?

• Conservative and Semiconservative Replication are two modes of DNA replication.
• In each method, two double helices form from old DNA molecule.

What is the Difference Between Conservative and Semiconservative Replication?

Conservative and semiconservative replication are two models out of the three models of DNA replication. Conservative replication would produce two helices, and among them, one contains entirely old DNA while the other contains entirely new DNA. Semiconservative replication is the accepted theory of DNA replication that produces two helices that contain one old strand and one new strand. When forming the new strand, there has to be a template strand for the DNA polymerase to add nucleotides in the semiconservative model. The below inforgraphic presents a detailed side by side comparison of the difference between conservative and semiconservative replication.

Summary – Conservative vs Semiconservative Replication

Conservative and semiconservative replication are two models proposed for DNA replication. In conservative replication, scientists believed that DNA does not unwind and while keeping them intact, new DNA helices form from old DNA. Hence, conservative replication results entirely one old DNA helix and one entirely new DNA helix. In semiconservative replication, each new helix formed contains one new strand and one old strand. Conservative replication model is not found to be biologically significant than semiconservative replication. Hence, this is the difference between conservative and semiconservative replication.

Reference:

1.“Molecular Mechanism of DNA Replication.” Khan Academy, Khan Academy. Available here  
2.“Semiconservative Replication.” Wikipedia, Wikimedia Foundation, 3 July 2018. Available here

Image Courtesy:

1.”DNA Replication Theories Map2″By Cjhiggin at English Wikibooks, (CC BY-SA 3.0) via Commons Wikimedia  
2.”DNAreplicationModes”By Adenosine at English Wikipedia. (CC BY-SA 2.5) via Commons Wikimedia 

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