Meselson and Stahl experiment | Conservative, Dispersive & Semiconservative DNA replication

Описание: Meselson and Stahl experiment. Conservative, Dispersive & Semiconservative DNA replication

This is the third class of Molecular basis of inheritance class 12 by Completely Biology. In this class you will get to know the models for DNA replication that is the Conservative Model, the Dispersive Model and the Semiconservative Model and Meselson–Stahl experiment which supported Watson and Crick's hypothesis that DNA replication occurs in semiconservative manner.

Meselson and Stahl extracted DNA and centrifuged on CsCl density gradient.

🔴 Why CsCl?

Cesium chloride (CsCl) is an inorganic, colourless, hygroscopic ( readily taking up and retaining moisture) compound and is highly soluble in water. Due to its hygroscopic characteristic, when put in water, it forms a dense solute that is not very viscous (sticky). Therefore, it is a good material for equilibrium gradient differential centrifugation where the separation of the particles is size and density dependent. The method is used to separate cellular compartments (organelles), different types of DNA (viral, plasmid, mitochondrial, etc.), or RNA types (mRNA, tRNA, and rRNA).

The separation of different types of DNA usually involves the centrifugation of the DNA resuspension layered on top of CsCl gradient, at a certain speed for a decided length of time.
Addition of ethidium bromide (EtBr) enhances the density difference between linear and circular/coiled DNA and also makes the bands formed after centrifugation visible under ultraviolet (UV) light.

Conservative Model- 01:32
Dispersive Model- 02:35
Semiconservative Model- 03:49
The Meselson-Stahl experiment- 04:50

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