You are analyzing a circular DNA plasmid that contains 1 Hin

You are analyzing a circular DNA plasmid that contains 1 HindIII site, 3 PstI sites, and 2 BamHI sites. How many fragments will you see when you cut with HindIII and BamHI?

1, 2, 3, 4, or 5?

Solution

The number of framents produced when a circular plasmid is cut at N restriction sites are N only.

ex.- if a single restriction site is present in the plasmid and cut at that, the circular plasmid cuts open and can be considered as a single linear fragment.

Here, in the problem the circular plasmid is being cut at 3 sites- 1 HindIII and 2 PstI sites. so the number of fragments produced will be three only irrespective of the type of restriction enzyme used.