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 sampleA).You then wash the remaining E.coli cells and grow them for one generation in ¹⁴N,extract the DNA from a portion of the culture,and determine its density to be 1.715 gm/cm³ (call this sampleB).You let the culture grow for one more generation in ¹⁴N and extract the DNA (call this sampleC)Each sample of DNA (A,B,and C)is then heated to completely denature the double-stranded structures,cooled quickly (to keep the strands separate),and subjected to ultracentrifugation.Present the centrifugation profiles for heat-denatured DNA (samples A,B,andC)that you would expect.Use the graph below.(Note: Although not the case,assume that single-stranded DNA has the same density as double-stranded DNA.)

Question

Assume that you grew a culture of E.coli for many generations in medium containing <sup>15</sup>N (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 sampleA).You then wash the remaining E.coli cells and grow them for one generation in <sup>14</sup>N,extract the DNA from a portion of the culture,and determine its density to be 1.715 gm/cm³ (call this sampleB).You let the culture grow for one more generation in <sup>14</sup>N and extract the DNA (call this sampleC)Each sample of DNA (A,B,and C)is then heated to completely denature the double-stranded structures,cooled quickly (to keep the strands separate),and subjected to ultracentrifugation.Present the centrifugation profiles for heat-denatured DNA (samples A,B,andC)that you would expect.Use the graph below.(Note: Although not the case,assume that single-stranded DNA has the same density as double-stranded DNA.)

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 sampleA).You then wash the remaining E.coli cells and grow them for one generation in ¹⁴N,extract the DNA from a portion of the culture,and determine its density to be 1.715 gm/cm³ (call this sample B).You let the culture grow for one more generation in ¹⁴N and extract the DNA (call this sample C)Each sample of DNA (A,B,and C)is then heated to completely denature the double-stranded structures,cooled quickly (to keep the strands separate),and subjected to ultracentrifugation.Present the centrifugation profiles for heat-denatured DNA (samples A,B,and C)that you would expect.Use the graph below.(Note: Although not the case,assume that single-stranded DNA has the same density as double-stranded DNA.)

Assume That You Grew a Culture of E