10. What percent of labeled cells are in M phase at 4 hours after exposure to labeled thymidine?
(A) 100
(B) 33
(C) 20
(D) 6
(E) 0

複選題6. Which of the following statements are true for the enzyme reverse transcriptase? (A) It is sensitive to high temperatures and so can be readily "killed" by heat treatment when the reaction is completed. (B) It does not require a primer to initiate polymerization as do most DNA polymerases. (C) It is insensitive to high temperatures and so can survive the many cycles of heating required to perform the polymerase chain reaction. (D) It is an RNA-dependent DNA polymerase. (E) It lacks the proofreading function of most DNA polymerases and so is able to utilize mRNA from mutated genes as a template. 

7. Possesses genes that may be integrated into the genome of an infected eukaryotic cell(A) E. coli (B) Yeast (C) Retrovirus (D) Bacteriophage lambda (E) Adenovirus

8. Can lysogenize bacteria(A) E. coli (B) Yeast (C) Retrovirus (D) Bacteriophage lambda (E) Adenovirus 

9. The reason it takes approximately one hour before the first radioactively labeled mitotic cells are observed is that (A) cells must repair thymidine-induced DNA damage before entering G2 (B) the cells get out of synchrony as they proceed through the cell cycle (C) the period of thymidine labeling is 5 minutes (D) G2 lasts 1 hr (E) M phase lasts 1 hr

11. If the length of G2 were increased by one hour, which of the following statements would be true regarding the slope of the line from the point of the first appearance of labeled mitotic cells to the first point at which all the mitotic cells were labeled? (A) It would stay the same. (B) It would decrease. (C) It would increase. (D) It would switch from a positive to a negative slope. (E) No conclusion regarding the slope of the line can be drawn.

12. The expected frequency of the triple CCC in the A: C=1:5 copolymer should be (A) 1/8 (B) 5/6 (C) 7/8 (D) 15/216 (E) 125/216

13. Which of the following amino acid(s) appear to be coded by triplets containing 2 A's and 1 C? (A) Asparagine (B) Glutamine (C) Proline (D) Threonine (E) Lysine 

14. Which mutant would have a mutation in the "strong" promoter? (A) 1 (B) 2 (C) 3 (D) 4 (E) 5

15. Which mutant(s) would have a mutation in the repressor? (A) 1 (B) 2 (C) 3 (D) 4 (E) 5

16. Which mutant(s) would have a mutation in the operator? (A) 1 (B) 2 (C) 3 (D) 4 (E) 5