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(i) Meselson & stahl used cesium chloride density gradient to distinguish heavy DNA molecules from the normal DNA molecules.
(ii) In meselson & Stahl experiment the DNA that was extracted from the culture one generation after the transfer from `.^(15)N` to `.^(14)N`, was composed of equal amount of hybrid (intermediate) DNA and of light DNA.
(iii) In prokaryotes, control f the rate of transcriptional initiation is the predominant site for control of gene expression.
(iv) In lac operon, the repressor is synthesised only at the time when the level of metabolite is in excess.
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