7. a. A culture of cells is grown inN15 continuously for several generations so thatvirtually all the DNA is N15. Similarly another cultureof cells is grown in N14 continuously for severalgeneration. DNA is extracted from each culture and equal amountsfrom each are mixed together. The mixture is then subjected to thefollowing treatment, it is heated at 100oC for severalminutes and allowed to cool back to room temperature so that theDNA can reanneal. The mixtures, both before and after the treatmentare analyzed by CsCl density gradientcentrifugation. What are the results in terms ofHeavy, Intermediate and Light molecules and their ratios, Beforeand After the above described treatment. Explain.
b. Aculture of cells grown continuously for several generations inN14 is switched to N15 and allowed toreplicate for only one round of DNA synthesis. DNA is extractedfrom the culture. The DNA is then treated as in part a:it is heated at 100oC for several minutes and allowed tocool back to room temperature so that the DNA can reanneal. The DNAsamples, both before and after the treatment are analyzed by CsCldensity gradient centrifugation. What are theresults in terms of Heavy, Intermediate and Light molecules andtheir ratios, Before and After the above described treatment.Explain.
7. a. A culture of cells is grown inN15 continuously for several generations so thatvirtually all the DNA is N15. Similarly another cultureof cells is grown in N14 continuously for severalgeneration. DNA is extracted from each culture and equal amountsfrom each are mixed together. The mixture is then subjected to thefollowing treatment, it is heated at 100oC for severalminutes and allowed to cool back to room temperature so that theDNA can reanneal. The mixtures, both before and after the treatmentare analyzed by CsCl density gradientcentrifugation. What are the results in terms ofHeavy, Intermediate and Light molecules and their ratios, Beforeand After the above described treatment. Explain.
b. Aculture of cells grown continuously for several generations inN14 is switched to N15 and allowed toreplicate for only one round of DNA synthesis. DNA is extractedfrom the culture. The DNA is then treated as in part a:it is heated at 100oC for several minutes and allowed tocool back to room temperature so that the DNA can reanneal. The DNAsamples, both before and after the treatment are analyzed by CsCldensity gradient centrifugation. What are theresults in terms of Heavy, Intermediate and Light molecules andtheir ratios, Before and After the above described treatment.Explain.
