Assume that a plasmid (circular) is 3200 base pairs in length and has restriction sites at the following locations: 400, 700, 1400, 2600. Give the expected sizes of the restriction fragments following complete digestion.

The options:

A) 400, 800, 1000 (2 of these)

B) 400, 1200, 1600

C) 300, 700, 2200

D)700, 400, 1400, 2600

E) 300, 700, 1000, 1200

The CORRECT ANSWER IS E)

E) 300, 700, 1000, 1200

Explanation:

The attached image shows a fragments produced after total digestion of the plasmid by restriction enzymes.

The distance which the base pairs is in relation to the restriction site at location 400 and 700 is 300, which is equal to the size of one of the produced fragments.

The following position of a restriction site is 1400, with a distance of 700 bp in relation to the previous site.

Next, we see 1200 bp distance between the restriction site at positions of 2600 and 1400.

Lastly, due to the circular nature of the plasmid we see no restriction site at the location 0 (or 3200), the last fragment tend to possess a length of: 3200 - 2600 + 400 = 1000 bp.

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