Difference between Conservative and Semiconservative Replication

Conservative Replication and Semiconservative Replication are the two proposed models of replication. In the DNA replication process of conservative replication, the original DNA remains intact and serves as a template for the synthesis of two new DNA molecules. 

In semiconservative replication, each original DNA strand serves as a template for the synthesis of a new strand, resulting in two DNA molecules, each with one original strand and one new strand. Semiconservative replication is the most accepted model of DNA replication. In this article, we will read about semiconservative and conservative replication and the differences between them.

Difference Between Conservative and Semiconservative Replication

The table given below summarises the key differences between Conservative and Semi-conservative Replication:

Features	Conservative Replication	Semiconservative Replication
Definition	In this type of replication, one entirely old and entirely new DNA is produced.	In this type of replication, both newly formed DNAs consist of one old and one new strand.
Type of Replication Model	It is a theoretical model of replication.	It is an actual proven model of replication.
Significance	It is not found to be biologically significant.	It is biologically significant.
Unwinding of Parent DNA	No unwinding of parent DNA occurs.	Parent DNA unwinds and opens for replication.
Role of Template Strand	Not clear	Each strand of the parent DNA molecule works as a template strand for the formation of a new strand.
Synthesis of New DNA Strand	New DNA strands are formed away from parental strands.	New DNA strands are formed alongside the parental strands.
DNA Helices	Out of the two DNA helices, one has entirely new DNA and the other has entirely old DNA.	Both DNA helices are made up of one new strand and one old strand.
Mechanism of Proofreading.	Lacks an efficient proofreading mechanism.	It has an efficient proofreading mechanism and is done by DNA polymerase.

What is Conservative Replication?

Conservative Replication is a theoretical model of replication. In this model of replication, the parent DNA strands stay together and work as a template for the synthesis of an entirely new DNA molecule. It is a hypothetical model in which two daughter DNA molecules are produced. Out of the two DNA helices, one DNA molecule contains entirely old or parental DNA and another contains entirely new DNA or daughter DNA. Hence, it can be said that this replication yields one “all-new” DNA and one “all-old” DNA.

This model of replication was proposed early and it is important to note that this type of replication is not seen in living organisms as it cannot ensure diversity and adaptability at the genetic level. Thus, it is not considered significant in biology. It is only a theoretical concept and was disapproved after the introduction of the Semiconservative model of Replication in 1958 backed by Meselson-Stahl’s experiment.

Significance of Conservative Replication

Although the conservative replication model has no biological significance, it has the following historical significance:

• This model was proposed early as one of the potential mechanisms by which genetic material could be duplicated.
• The conservative replication model helped the researchers and the scientists to understand the process /mechanism of DNA replication.
• It motivated them to do experiments and investigations to understand and discover the actual mechanism of DNA replication.
• The Conservative replication model has worked as a stepping stone in the understanding of the DNA replication mechanism.
• This model led to the discovery of the semi-conservative model of replication.

What is Semiconservative Replication?

The semiconservative replication model is the most accepted model of replication. In this model, each of the two strands of the DNA molecule serves as a template for new DNA synthesis, and thus each newly produced DNA molecule consists of one new strand and one old strand. By “semi-conservative” it means during the replication process, the parental DNA subunits are conserved and equally distributed among the daughter molecules.

Meselson and Stahl in 1958, confirmed this model based on a series of experiments that involved growing Escherichia coli. To trace the replication process, E. coli was grown for many generations in a medium containing the isotopes of nitrogen, (Nitrogen-14- the common and lighter isotope, and Nitrogen-15 -the rare and heavier isotope) in the form of 15NH4Cl. Meselson and Stahl chose the isotopes of Nitrogen for the experiment because of the presence of Nitrogen in DNA as an important chemical component. Today, the semi-conservative model of replication has become a universal mechanism and is shared by all organisms present on the earth.

Significance of Semiconservative Replication

Semiconservative replication is an important model of DNA replication. It explains the formation of a daughter strand from a template strand. Hence, each newly formed DNA has one old and one new strand. It has several significances. For example,

• Biological significance: This model reflects the actual mechanism of DNA replication in living organisms and is experimentally proved by the famous Meselson-Stahl experiment. Hence. It is biologically significant.
• Conservation of Genetic information: Semiconservative replication ensures the conservation of half of the original DNA. By conserving half of the parental DNA it ensures genetic continuity.
• Adaptability and Evolution: Semiconservative replication allows recombination and genetic variation through mutations in the newly synthesized strands. This variability is important for the adaptability of populations over generations and contributes to the process of evolution.
• Reduced error and easy repair mechanism: Semiconservative replication is a fast, accurate method that also provides easy repair of DNA.

Conclusion: Conservative and Semiconservative Replication

Conservative and Semiconservative Replication are the two proposed models of replication. There are significant difference between Conservative and Semiconservative Replication of DNA. In the conservative replication model, DNA helices do not unwind and produce one entirely new and one entirely old helix. In semiconservative replication, the strands work as template strands and form new helices. Each of the helix has one new strand and one old strand. Semiconservative replication gives a clear explanation of the unwinding of DNA. It is the actual process by which DNA replicates inside the cell, hence it is considered a biologically significant method.

FAQs on Conservative and Semiconservative Replication

What is Dispersive Replication?

Dispersive replication is the third model of replication. In this model of replication, each strand of the newly produced has alternate old and new DNA segments.

What is the Difference Between Conservative and Semi-Conservative Replication?

In conservative replication, out of two newly produced double helices, one helix contains entirely old DNA and the other helix contains entirely new DNA. The old parental DNA remains intact. In semi-conservative replication, each strand of the two newly formed DNA has one old strand and one new strand.

Why is Semiconservative Replication Considered the Best Replication?

Semiconservative replication conserves genetic information, allows genetic diversity, contributes to evolution, and is also a fast and accurate method that provides easy DNA repair. Thus it is considered the best replication.

What is the Fidelity of Replication?

The fidelity of replication refers to the accuracy with which DNA is replicated, ensuring minimal errors in the process.

What are the Three Types of DNA Replication?

The different types of DNA replication are Conservative replication, Semiconservative replication, and Dispersive replication.

Who Proposed the Semiconservative Replication Theory?

The semiconservative replication theory was proposed by Matthew Meselson and Franklin Stahl in 1958. It is the actual and proven method of replication.

Is DNA Replication Semiconservative and Discontinuous?

Yes, DNA replication is semiconservative, with one parental and one newly synthesized strand. It is continuous on the leading strand but discontinuous, forming Okazaki fragments, on the lagging strand.

What is a DNA Replication Fork?

A DNA replication fork is a Y-shaped structure formed during DNA replication, where the double-stranded DNA molecule unwinds and separates into two single strands.

How does DNA Replication in Prokaryotes Occur?

In prokaryotes, DNA replication is initiated at a single origin of replication and proceeds bidirectionally, forming replication forks where DNA polymerases synthesize new DNA strands.

What is the Use of Helicase?

Helicase is an enzyme that plays a crucial role in DNA replication by unwinding the double-stranded DNA molecule, separating it into two single strands, and forming replication forks for DNA polymerases to synthesize new DNA strands.