Matthew Meselson and Franklin Stahl demonstrated that DNA replication is semiconservative in bacteria.Choose the correct description of their experiment.A. Meselson and Stahl initially cultured E. coli in medium containing only 15N until all cells contained only 15N/15N DNA. They then cultured the 15N/15N E. coli in normal medium (14N) and collected samples after one, two, and three rounds of DNA replication.B. Meselson and Stahl initially cultured E. coli in medium containing both 14N and 15N until all cells contained only 14N/15N DNA. They then cultured the 14N/15N E. coli in normal medium (14N) and collected samples after one, two, and three rounds of DNA replication.C. Meselson and Stahl initially cultured E. coli in medium containing both 14N and 15N until all cells contained only 14N/15N DNA. They then cultured the 14N/15N E. coli in medium containing only heavy nitrogen (15N) and collected samples after one, two, and three rounds of DNA replication.D. Meselson and Stahl initially cultured E. coli in medium containing only 15N until all cells contained only 15N/15N DNA. They then cultured the 15N/15N E. coli in medium containing both 14N and 15N and collected samples after one, two, and three rounds of DNA replication.

They selected the E.coli bacteria and grew them in the heavy isotope of Nitrogen that is N¹⁵ and later into the N¹⁴ isotope. Since nitrogen is the constituent of the DNA, therefore, is incorporated into the DNA.

They used the CsCl density centrifugation technique and observed the bands according to the density of nitrogen and reached the conclusion after the third generation that DNA replicates by semiconservative mode.

Thus, Option-A is correct.