28. Epigenetic modulation can control gene expression without changing DNA
sequences. Please explain how this is achieved (5 points).

C. 5'-AGAGCTAGATCGAT-3'
3'-TCTCGATCTAGCTA-5'

B. 5'-ATTATAAAATATTTAGATACTATATTTACAA-3'
3'-TAATATTTTATAAATCTATGATATAAATGTT-5'

40. In order for lysogeny to occur, the enzyme
bacterial chromosome.
(A) ligase
(B) lysogenase
(C) helicase
(D) integrase
must insert the phage DNA into a specific site in the

39. Which of the following the represents the correct sequence of events for the Holiday model of homologous
recombination?
(A) nicking, strand invasion, branch migration, ligation, crossed strand breakage, rejoining
(B) nicking, strand invasion, branch migration, crossed strand breakage, ligation, rejoining
(C) nicking, strand invasion, ligation, branch migration, crossed strand breakage, rejoining
(D) nicking, strand invasion, ligation, branch migration, isomerization, crossed strand breakage, rejoining

38. Which of the following exonuclease activities is present in DNA polymerase I?
(A) 3'exonuclease that degrades double stranded DNA
(B) 3'exonuclease that degrades hairpin DNA
(C) 5'exonuclease that degrades single stranded DNA
(D) 5'exonuclease that removes RNA from a DNA-RNA duplex