Question

For questions 13 and 14. Your microbiologist sweetheart studies an odd strain of bacteria that maintains plasmid DNA in a fully relaxed state, meaning there is neither positive nor negative supercoiling in any plasmid DNA isolated from this strain. As a token of affection s/he gifts you a sample of plasmid DNA that has been purified such that all the plasmid DNA is cate nated with other plasmid molecules. This, you are told, is a molecular representation of your special relationship: free to tumble and rotate and explore space as beautiful individuals, but always together in the end After breaking up a week later, you discover leftover nickase enzyme from your previous experiment. Driven by curiosity (and bitterness) DNA sample with nickase enzyme. . you decide to treat some of the special 13 When you examine both nicked and untreated DNA side-by-side using gel electr rophoresis, what are you most likely to observe? (Remember, your special plasmid DNA sample is fully relaxed and every plasmid molecule is catenated with another) A) Nicked plasmid DNA travels faster through the gel B)Nicked plasmid DNA travels slower through the gel -C) Nicked plasmid DNA travels at the same rate as the untreated DNA icked plasmid DNA is no longer visible because ethidium bromide will no longer be able to bind Suggestion: consider drawing your DNA samples before answering the ques tion. A. You and catenated plasmid sample. When you examine both treated and untreated DNA side- by-side using gel electrophoresis, what are you most likely to observe? u also find some topoisomerase Il in your freezer and again treat your fully relaxed Compared to untreated DNA, topisomerase Iltreated DNA travels. A)...faster through the gel slower through the gel C) ...at the same rate as the untreated DNA D) Topoisomerase Il-treated plasmid DNA is no longer visible because ethidi will no longer be able to bind

please answer #13 & #14

Answer 1

Answer

13. Option B is the right answer as nicked DNA move slower as comparision to supercoild or linear DNA becasue nicked nicking in one strand makes DNA relax and circular which makes larger molceule and difficult to move in the gel.

14. Option A is the right answer as topoisomerase II introdiuce the negative supercoil in the DNA which makes DNA more compact hence easy to move in the agarose gel and faster as well.