Provide experimental evidence for semi conservative mode of replication. Meselson and Stahl in 1957 gave experimental evidences that each DNA strand served as a template for new synthesis, a process called semi conservative replication.
Answers
eselson-Stahl experiment
A key historical experiment that demonstrated the semi-conservative mechanism of DNA replication.
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Key points:
There were three models for how organisms might replicate their DNA: semi-conservative, conservative, and dispersive.
The semi-conservative model, in which each strand of DNA serves as a template to make a new, complementary strand, seemed most likely based on DNA's structure.
The models were tested by Meselson and Stahl, who labeled the DNA of bacteria across generations using isotopes of nitrogen.
From the patterns of DNA labeling they saw, Meselson and Stahl confirmed that DNA is replicated semi-conservatively.
Mode of DNA replication
Imagine yourself in 1953, after the double helix structure of DNA has just been discovered^1
1
start superscript, 1, end superscript. What burning questions might be on your mind, and on the minds of other scientists?
One big question concerned DNA replication. The structure of the DNA double helix provided a tantalizing hint about how copying might take place^{1,2}
1,2
start superscript, 1, comma, 2, end superscript. It seemed likely that the two complementary strands of the helix might separate during replication, each serving as a template for the construction of a new, matching strand.
But was this actually the case? Spoiler alert: The answer is yes! In this article, we'll look at a famous experiment, sometimes called "the most beautiful experiment in biology," that established the basic mechanism of DNA replication as semi-conservative—that is, as producing DNA molecules containing one new and one old strand^3
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cubed.