1. What is the purpose of the electrophoresis of DNA in general? 2. Which electr
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Question
1. What is the purpose of the electrophoresis of DNA in general? 2. Which electrode does DNA move toward? Why? 3. Where in the gel will we find the shortest DNA fragments? Why did we need to use PCR on our DNA first? What would we expect to see in the gel if the PCI not work at all? 4. 5. What would we expect to see in the gel if the PCR worked, but restriction digest did not? 6. What is the purpose of the pBR322/BstNI marker ladder? gel? 7. What 2 things do we need to make the DNA visible in the 8. Why do we expect each lane to have only one, two or three bands?Explanation / Answer
1. The DNA electrophoresis is used to separate macromolecules like DNA, RNA etc. DNA fragments are separated based on their size. The electrophoresis can used as a diagnostic tool to visualize the fragments.
2. DNA is negatively charged due to all the phosphate groups on the backbone, thus it will move towards the positive electrode.
3. The smaller fragments of DNA can esaily move through the pores of agarose gel and can be found on the lower side of gel i.e. opposite of the wells in which DNA is loaded.
4. PCR is used to amplify of a single fragment of DNA many times so that it can be seen on agarose gel. If PCR does not work at all, you will not see any DNA fragment on the gel.
5. Undigested plasmids run on gel as three bands which include uncut relaxed, uncut supercoiled plasmid.
6. pBR322/BstNI DNA yields 6 fragments suitable for use as molecular standards for agarose gel electrophoresis.
7. Two things needed for DNA to be visible on gel include DNA stain like EtBr and electric field.
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