Semiconservative replication

Semiconservative replication is a method of DNA replication in which the original strands of DNA are separated, each serving as a template for the synthesis of a complementary strand. This process results in two copies of the original DNA molecule, each containing one of the original strands and one new strand. This method of replication was first demonstrated by Matthew Meselson and Franklin Stahl in 1958.

Overview[edit | edit source]

Semiconservative replication begins with the unwinding of the double helix to expose the bases in each strand of DNA. This is facilitated by the enzyme helicase. The unwinding of the helix creates a 'Y' shaped structure known as a replication fork.

At the replication fork, the enzyme DNA polymerase begins to synthesize a new strand of DNA using the original strand as a template. The synthesis of the new strand occurs in the 5' to 3' direction. This means that the new strand is synthesized in a direction opposite to the way the original strand is read.

The result of semiconservative replication is two DNA molecules, each composed of one original strand and one newly synthesized strand. This ensures that the genetic information is preserved and accurately passed on to the next generation.

Meselson-Stahl Experiment[edit | edit source]

The semiconservative model of DNA replication was first proposed by James Watson and Francis Crick. However, it was the Meselson-Stahl experiment that provided the experimental evidence to support this model.

In their experiment, Meselson and Stahl grew bacteria in a medium containing a heavy isotope of nitrogen (Nitrogen-15). They then transferred the bacteria to a medium containing a lighter isotope (Nitrogen-14). After several generations, they extracted the DNA from the bacteria and analyzed it using density gradient centrifugation.

The results of the experiment showed that the DNA extracted from the bacteria contained a mixture of heavy and light DNA, supporting the semiconservative model of DNA replication.

References[edit | edit source]

Semiconservative replication Resources
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