The key difference between conservative semiconservative and dispersive replication is in the type of DNA helices they produce. Conservative replication produces two DNA helices in which one helix contains entirely old DNA, and the other helix contains entirely new DNA while semiconservative replication produces two helices in which each helix contains one new strand and one old strand; dispersive replication, on the other hand, produces two helices in which each strand contains alternating segments of old and new DNA.
DNA mainly exists as a double helix comprised of two complementary strands. DNA replication is the process of producing replicas or identical copies of DNA from original DNA molecules. It is an extremely important process that facilitates the passing of genetic material from parent to offspring. In other words, DNA replication is the basis of heredity or biological inheritance. There are three postulated methods of DNA replication as semiconservative replication, conservative replication, and dispersive replication.
CONTENTS
1. Overview and Key Difference
2. What is Conservative Replication
3. What is Semiconservative Replication
4. What is Dispersive Replication
5. Similarities Between Conservative Semiconservative and Dispersive Replication
6. Side by Side Comparison – Conservative vs Semiconservative vs Dispersive Replication in Tabular Form
7. Summary
What is Conservative Replication?
Conservative replication is one of the three models of DNA replication. This process produces two DNA helices from one original DNA helix. Out of the two helices formed, one helix contains entirely old or parental DNA while the other helix contains entirely new DNA.
Figure 01: Three Replication Models
Furthermore, this mode of replication is not found to be biologically significant. Scientists believed that parental DNA does not split open up in this model at all. They also argued that entirely new and separate copy of DNA forms in this model, somehow keeping parent strands intact.
What is Semiconservative Replication?
Semiconservative replication is the biologically significant model of DNA replication proposed by Watson and Crick in 1953. In this method, out of two helices formed, each helix contains one new strand and one old or parental strand. According to Watson and Crick, during semiconservative replication, one old DNA strand serves as a template to form the new strand. Hence, each new double helix produced contains one old DNA strand every time.
Figure 02: Semi Conservative Replication
Therefore, this model of DNA replication is considered to be more rational than the other two models. It is because 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 is Dispersive Replication?
Dispersive replication is the third possible model of DNA replication. The model produces DNA helices that contain a mixture of old and new DNA. Thus, each new strand in the helix is a patchwork of old and new DNA. In simple words, all strands in the DNA helices contain alternating parental and new DNA segments, as explained in this model. Scientists believe that DNA only copy itself for short chunks at a time to produce an alternating pattern of DNA.
What are the Similarities Between Conservative Semiconservative and Dispersive Replication?
- Conservative, semiconservative and dispersive replication are three models of DNA replication.
- All models produce DNA helices containing two complementary strands.
What is the Difference Between Conservative Semiconservative and Dispersive Replication?
Conservative replication produces two helices, one containing entirely old DNA while the other containing entirely new DNA. Semiconservative replication is the accepted theory of DNA replication that produces two helices, each containing one old strand and one new strand. Dispersive replication, on the other hand, produces two helices in which each strand contains alternating segments of old and new DNA. So, this is the key difference between conservative semiconservative and dispersive replication.
Summary – Conservative Semiconservative vs Dispersive Replication
There are three models that describe DNA replication in living organisms. They are conservative replication, semiconservative replication, and dispersive replication. Conservative replication produces one helix containing entirely old DNA and other helix containing entirely new DNA. In contrast, the semiconservative model produces two helices, and each has one strand of old DNA and one strand of new DNA. Meanwhile, the dispersive model produces DNA helices in which each strand has alternating segments of new and old DNA. So, this is the key difference between conservative semiconservative and dispersive replication.
Image Courtesy:
1. “Semi-Conservative DNA Replication: Meselson and Stahl.” Nature News, Nature Publishing Group, Available here.
2. “Mode of DNA Replication: Meselson-Stahl Experiment.” Khan Academy, Available here.
Image Courtesy:
1. “DNAreplicationModes” By The original uploader was Adenosine at English Wikipedia. – Transferred from en.wikipedia to Commons (CC BY-SA 2.5) via Commons Wikimedia
2. “Semiconservative replication” By Lizanne Koch – lgkoch – own work with chemdraw (Public Domain) via Commons Wikimedia