You have some circular DNA in a tube and wish to introduce negative supercoils into it. However, you ran out of topoisomerase. Can you think of a way to do this usingDNA ligase and ethidium bromide

Question

Biology

Cyrus Beasley

26 August, 04:04

You have some circular DNA in a tube and wish to introduce negative supercoils into it. However, you ran out of topoisomerase. Can you think of a way to do this usingDNA ligase and ethidium bromide

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Answers (2)

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Halle Schwartz · Answer 1

Digest With restriction enzyme to linearize, ligate the DNA with the EtBr present (will generate circles), then remove the EtBr by extraction (butanol for example). The DNA will now be negatively supercoiled since Tw + Wr = constant.; )

Winston Meadows · Answer 2

First the DNA ligase will join the DNA together.

Secondly, ethidium bromide is added to generate circles after then it is extracted.

After these are done, the DNA becomes negatively supercoiled since

Tw + Wr = constant.

Tw = twist

Wr = writhe