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DNA Topology and Electrophoresis

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Questions and Answers

What is the primary purpose of using ethidium as a stain in DNA visualization?

To reduce the twist of DNA
To fluorescently label DNA under ultraviolet light (correct)
To break covalent bonds in DNA
To increase the linking number of cccDNA

What happens to the helical pitch of linear DNA when ethidium binds to it?

It decreases significantly
It increases dramatically (correct)
It remains unchanged
It increases slightly

What is the effect of ethidium intercalation on the twist of DNA?

It decreases the twist (correct)
It changes the direction of the twist
It increases the twist
It has no effect on the twist

What happens to the linking number of cccDNA when ethidium binds to it?

It remains the same (D) Signup and view all the answers

What is the result of adding ethidium to negatively supercoiled DNA?

It becomes relaxed (B) Signup and view all the answers

What happens to the writhe of DNA when ethidium binds to cccDNA?

It increases (A) Signup and view all the answers

What is the significance of the 26° decrease in twist angle when ethidium intercalates between base pairs?

It indicates DNA unwinding (A) Signup and view all the answers

What would be the effect of adding an extremely large amount of ethidium to a circular DNA molecule?

It would become extremely positively supercoiled (D) Signup and view all the answers

What is the role of ethidium in gel electrophoresis?

It is a DNA staining agent (D) Signup and view all the answers

What is the fate of the twist of DNA when an ethidium ion intercalates between two base pairs?

It decreases by 26° (C) Signup and view all the answers

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