Question

1. Imagine you have a plasmid and you cut it with three different restriction enzymes (enzymes 1, 2, 3). You then run these fragments through a gel and get this separation. (10 pts)
   1. Label the positive and negative terminals on this gel with a (+) and (-) sign.

2. If you were working with a single plasmid, how many cut sites did restriction enzyme 1 have? Explain?

3. When creating a gel, we stain it with Ethidium Bromide or Gel Red. What is the purpose of this? Explain.

Answer 1

Answer a. On the gel, where the DNA is loaded marked the - end as DNA is negatively charged, the opposite to this is the + end. As gel electrophoresis ends, all smallest fragments are seen at the positive end and largest ones at the negative end.

Answer b. A restriction enzyme acts at a specific recognition sequence with a specific restriction site. If two bands are observed on gel then it means that one cut has been made by the restriction enzyme.

Answer C. As DNA movement gets over in the gel, the last step remains is to separate them. This process is known as elution. It is generally done using ethidium bromide.

The separated dna fragments are then used for various biotechnological purposes.