SAT Subject Biology Practice Question 397: Answer and Explanation
7. What fragments would be produced if the following plasmid were to be digested with EcoRI and HindIII to completion?
A. 200 kb and 300 kb
B. 200 kb, 300 kb, and 475 kb
C. 600 kb, 475 kb, 375 kb, and 500 kb
D. 200 kb, 300 kb, 400 kb, and 75 kb
E. 200 kb and 775 kb
Correct Answer: B
B Note that the plasmid has EcoRI sites, a HindIII site, and a PstI site. Because only EcoRI and HindIII are used, only those sites will be cut; the PstI site will effectively be ignored. To "digest to completion" means that the plasmid will be cut completely at those restriction sites. Three fragments will be produced, each corresponding to the distance (in kb) between the EcoRI and HindIII sites.