A particular virus that infects E. coli does so by integrati…
A particular virus that infects E. coli does so by integrating its DNA into the bacterial DNA. How well this integration goes depends on the topology of the E. coli ‘s DNA. If the superhelical density (σ) of the E. coli DNA is greater than −0.045, the probability of integration is less than 20%. However, when σ is less than −0.06, this probability is >70%. Show your work. The bacterial DNA isolated from an E. coli culture is found to have a length of 13,800 bp and an Lk of 1,222. a) Explain why σ is typically a negative number in cells. b) Calculate σ for this bacterial DNA. Show your work. c) Predict the likelihood that the virus will be able to integrate its DNA into the E. coli genome.
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