Genetics: Analysis and Principles 5th Edition by Robert Brooker

Exercise 36

Table 20.3 describes the cleavage sites of five different restriction enzymes. After these restriction enzymes have cleaved the DNA, four of them produce sticky ends that can hydrogen bond with complementary sticky ends, as shown in Figure 20.1. The efficiency of sticky ends binding together depends on the number of hydrogen bonds; more hydrogen bonds makes the ends "stickier" and more likely to stay attached. Rank these four restriction enzymes in Table 20.3 (from best to worst) with regard to the efficiency of their sticky ends binding to each other.Table 20.3 Some Restriction Enzymes Used in Gene Cloning

a.
FIGURE 20.1 The action of a restriction enzyme and the production of recombinant DNA. The restriction enzyme Eco RI binds to a specific sequence, in this case 5 -GAATTC-3 . It then cleaves the DNA backbone between G and A, producing DNA fragments. The single-stranded ends of different DNA fragments can hydrogen bond with each other, because they have complementary sequences. The enzyme DNA ligase then catalyzes the formation of covalent bonds in the DNA backbones of the fragments.