You have a mixture of the plasmid shown below. Half of
the plasmid mixture is incubated with the enzyme EcoRI methylase. You
then add the three restriction endonucleases PstII, EcoRI, and
EcoRII to both the methylase-incubated and the unincubated plasmid
mixtures. Locations of the recognition sequences of these enzymes are shown
on the restriction map with distances in kilobases (kb). Later, you use electrophoresis
to examine the fragments produced. On the left, select a fragment that should
be present in the plasmid mixture that was incubated with EcoRI methylase, but absent in the unincubated mixture.
