Assume that you grew a culture of E. coli for many generations in medium containing 15N (from the ammonium ion), a heavy isotope of nitrogen. You extract DNA from a portion of the culture and determine its density to be 1.723 gm/cm3 (call this sample
A). You then wash the remaining E. coli cells, grow them for one generation in 14N,
and extract the DNA from a portion of the culture (call this sample
B). You let the
culture grow for one more generation in 14N and extract the DNA (call this sample
C) is then subjected to ultracentrifugation. Present the centrifugation profiles that you would expect under (a) semiconservative replication
and (b) conservative replication. (Note: Assume that unlabeled [14N] DNA has a density of 1.700 gm/cm3.)
C). Each sample of DNA (A, B, and

Question

Quizplus · Accepted Answer

The Answer of Assume that you grew a culture of E. coli for many generations in medium containing 15N (from the ammonium ion), a heavy isotope of nitrogen. You extract DNA from a portion of the culture and determine its density to be 1.723 gm/cm3 (call this sample
A). You then wash the remaining E. coli cells, grow them for one generation in 14N,
and extract the DNA from a portion of the culture (call this sample
B). You let the
culture grow for one more generation in 14N and extract the DNA (call this sample
C) is then subjected to ultracentrifugation. Present the centrifugation profiles that you would expect under (a) semiconservative replication
and (b) conservative replication. (Note: Assume that unlabeled [14N] DNA has a density of 1.700 gm/cm3.)
C). Each sample of DNA (A, B, and

Assume That You Grew a Culture of E