(a)Why did Meselson and Stahl use isotopes in the sources of nitrogen present in the culture medium in their experiment?
(b)Write the conclusion drawn by them from the experiment.
(a) Meselson and Stahl use isotopes in the sources of nitrogen present in the cultiure medium in their experiment as nitrogen is a major constituent of DNA.Morever is by far the moxt abundant isotope of nitrogen, nad DNA with the heavier. isotope is also functional.E.coli can be grown for several generations in a medium with easily. When DNA is extracted from these cells and centrifuged on a salt density gradient, the DNA separates out at the point at which its density equals that of the salt solution.
(b) The experiment proves the semi-conservative replication of DNA.In tjis type of replication, one strand of parent is new and one strand is old.It means, one strand of daughter duplex is derived from the parent, while the other strand is formed new.