In the classic experiment by Meselson and Stahl, E. coli cells completely labeled with ¹⁵ N were transferred to a medium containing normal ¹⁴ N . If the mechanism of DNA replication were strictly conservative instead of semiconservative, what would be the expected density distribution of DNA after exactly one generation of growth?

Step-by-step solution

In the conservative model of DNA replication, the parental DNA double helix remains completely intact, and an entirely new double helix is synthesized from the available nucleotides in the medium. Initially, the cells contain only heavy DNA ( ¹⁵ N / ¹⁵ N ). When transferred to a medium containing light nitrogen ( ¹⁴ N ) and allowed to replicate for one generation, the original heavy DNA molecules would be conserved, and the newly synthesized DNA molecules would be entirely light ( ¹⁴ N / ¹⁴ N ). As a result, the DN