In DNAhybridization experiments on six species of plants in

In DNA-hybridization experiments on six species of plants in the genus Vicia, DNA was isolated from each of the six species, denatured by heating, and sheared into small fragments (W. Y. Chooi. 1971. Genetics 68:213–230). In one experiment, DNA from each species and from E. coli was allowed to renature. The graph below shows the results of this renaturation experiment.

(Problem 37a) In DNA-hybridization experiments on six species of plants in the genus Vicia, DNA was isolated from each of the six species, denatured by heating, and sheared into small fragments (W. Y. Chooi. 1971. Genetics 68:213–230). In one experiment, DNA from each species and from E. coli was allowed to renature. The graph below shows the results of this renaturation experiment. Can you explain why the E. coli DNA renatures at a much faster rate than does DNA from all of the Vicia species?

The E. coli DNA sequences renature faster because the smaller E. coli genome results in a higher copy number than the plant DNA sequences for the same amount of DNA. The E. coli DNA sequences renature faster because they contain a higher amount of repetitive DNA sequences than plant DNA. The E. coli DNA sequences renature faster because the E. coli genome is circular. The E. coli DNA sequences renature faster because the E. coli genome has a higher percentage of G-C base pairs than plant DNA. The E. coli DNA sequences renature faster because the E. coli genome is adapted to living in a warm (37°) environment of the mammalian gut, and chemical reactions proceed faster at higher temperatures.

100 80 :S s =$ s+2 60 40 20 0246810 12 14 24 Time (hours) 1 = v. melanops, 2 = V. sativa, 3 = v. benghalensis, 4 = V. atropurpurea, 5 = V. faba, 6 = V. narbonensis, 7 = E. coli 1 2345 6 7 ne en v. e =6 Ill/V / 0 er paz-puqAu 10u e--= YNa palaqe-JO a6e Juaiad K14

Solution

Answer: (A)

The E. coli DNA sequences renature faster because the smaller E. coli genome results in a higher copy number than the plant DNA sequences for the same amount of DNA.

Explanation:

The E. coli genome is far smaller than the genomes of the plant species and therefore has lower complexity. Given the same concentration of DNA, the E. coli DNA sequences are at higher copy number than the plant DNA sequences, and therefore renature faster.