Question

A circular molecule has two sites for the restriction enzyme PstI and one site for the enzyme BamH1. How many fragments will result when digested with both enzymes?

Answer 1

Digesting a circular molecule with two PstI sites and one BamHI site using both enzymes will result in three DNA fragments, due to each enzyme's site-specific cutting actions.

Step-by-step explanation:

When digesting a circular molecule with two PstI sites and one BamHI site using both enzymes, the number of fragments produced will be three. PstI will cut at its two sites, and BamHI will cut at its single site. Given that the molecule is circular, each cut opens it into a linear form. The first cut by PstI would linearize the circle, and the second PstI cut plus the BamHI cut would then result in a total of three fragments. Each restriction enzyme recognizes specific sequences and creates sticky ends that can reattach to complementary sequences or can be ligated to form recombinant DNA.