If a restriction enzyme is used to digest both a closed circular DNA plasmid and a linear DNA strand with five recognition sites each, how many fragments will be produced in total?

11

The correct answer is Option (2) -11

To determine the number of fragments produced when a restriction enzyme digests a circular DNA molecule and a linear DNA molecule, we need to consider the number of recognition sites and the type of DNA molecule.

Circular DNA Molecule:

For a closed circular DNA molecule with 5 recognition sites:

• Each cut made by the restriction enzyme will break the circle, creating a fragment.
• Since it is circular, cutting it at 5 sites will produce 5 fragments.

Linear DNA Molecule:

For a linear DNA molecule with 5 recognition sites:

• Each cut will produce a new fragment, but since the DNA is linear, the first cut divides it into 2 pieces, and each subsequent cut adds one more piece.
• Cutting it at 5 sites will produce 6 fragments.

Total Number of Fragments:

• From the circular DNA: 5 fragments
• From the linear DNA: 6 fragments

Thus, the total number of fragments generated will be:

5 (from circular DNA)+6 (from linear DNA)=11