How DNA Replicates Itself.

How scientists came to find out how DNA replicated itself and conflicting theories.

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How DNA Replicates Itself?
There were many ideas of how DNA replicated itself after Watson and Crick
discovered the structure of it. Two of which were the conservative replication
and semi-conservative replication.
Conservative Replication
This idea suggested that the original somehow instructed another one to be
formed exactly the same as the original. The process didn't use any part of the
original part in any way it was just instructed.
Semi-Conservative Replication
This theory said how the DNA used half of itself to make a second strand exactly
the same as the original. This meant that both of the daughter strands included
half the original and the other half from free nucleotides.
The Test
Meselson and Stahl did a series of experiments to discover how DNA replicated.
First they grew DNA from bacteria in a radioactive isotope of Nitrogen (N15) for
many generations to ensure that it was 100% N15. Then they put the DNA in a
medium of the normal isotope of Nitrogen (N14) and found that after the first
generation the density was the same for both daughters. This suggests ad
proves that they were made by semi-conservative replication. A 2nd generation
was tested from the daughters and yet again the density was half again,
supporting the 1st
part of the experiment.
From this experiment we a rule out the conservative replication idea and believe
that the semi-conservative theory to be true.


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