chapter+5

Chargaff's Data.
1.   The ratio of A:T in humans and wheat is the same, that is 1.00 There is a rough equivalence of the ratio of G:C in wheat and human 0.98:1.00 Again the ratio of Purines and Pyramidines is roughly equivalent between wheat and humans 0.99:1.00

However the A:G and T:C ratios between humans and wheat are different. 2.   (a) The exact ratio of 1:1 is only found in Ox and Human. There is a range of results between 0.86-1.08 in all species tested. Across the species there a rough equivalence of 1:1 (b) The range of the ratios between purines and pyramidines is narrow 0.9 to 1.02 (c) Range is 0.95 to 1.12 , toc

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A DNA molecule composed of only N-14 should have a peak at 1.710; After one generation grown in N-14, there was no peak at 1.710; Therefore replication is not conservative; If dispersive, no matter how many generations, all molecules would have same ration of N-14 to N-15; Not dispersive as there would always be only one peak and second generation grown in N-14 has two peaks;

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1. More radioactive fragments of all sizes at 30 seconds; Increase in ratio of larger fragments to smaller fragments at 30 seconds/2 peaks at 30 seconds versus one peak at 10 seconds;

2. Two peaks suggests two different sizes of molecules predominate; Higher peak represents large number of small fragments/lagging strands; Smaller peak represents a number of longer fragments/leading strands;

3. If lagging strands are joined together by DNA ligase; Then the number of initial small molecules would decrease; and the number of larger molecules would increase; This is what is observed so the hypothesis is supported.