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.

Also Read: Genetic Drift – Definition, Types & Examples

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.

Also Read: Topoisomerase​

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.