Question

8. A circular plasmid of 6200 base pairs (bp) with three restriction enzyme sites at 900, 1300, and 4000 bp. You digest this plasmid, then run the digest on a gel. What are the expected DNA fragment sizes?

9. A linear plasmid of 6200 base pairs (bp) with three restriction enzyme sites at 900, 1300, and 4000 bp. You digest this plasmid, then run the digest on a gel. What are the expected DNA fragment sizes?

10. In a random sequence consisting of equal proportions of all four nucleotides, what is the average distance between restriction enzymes for a restriction enzyme with a 4-base cleavage site (hint- look for a similar problem in your book).

Answer 1

Q.8 Plamid is extrachromosomal genetic material present in bacteria. It is used as vector in recombinant DNA technology.

In this question Plamid is circular so number of fragments produced by cleavage will be equal to number of restriction sites it has.This is because plasmid is not linearised if we cleave it with one restriction enzyme it will produce only one fragement i.e become linearised. It give rise to three fragments of 400 bp, 2300 bp and 3100 bp as shown in figure below

Q.9 In this case plasmid is same but it is already linearized so it will produce four fragments of sizes 900 bp, 400 bp, 2700 bp and 2200 bp as shown in image below