A bacteria culture is grown for many generations in a medium inwhich the only available nitrogen is the heavy isotope(15N). The culture is then switched to a mediumcontaining only 14N for TWO generation of growth; it isthen recultured to a 15N-containing medium for ONE finalgeneration of growth. The DNA from these bacteria is isolated andcentrifuged to equilibrium in a CsCl density gradient.
(a) Determine the proportion of 15N15N,15N14N, and 14N14N DNA if thereplication is following the semiconservative mode. Show your workto gain maximum mark.
(b) Determine the proportion of 15N15N,15N14N, and 14N14N DNAif the replication is following the conservative mode. Show yourwork to gain maximum mark.
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