Mcb 250 Practice Exam3

MCB 250 Fall Semester 2012 Practice Examination 3 Instructions: Read each question and its accompanying choices CAREFULLY. Select the choice that is the BEST answer. 1. Which of the following statements concerning non-homologous end joining (NHEJ) is correct? A. B. C. D. E. (C) NHEJ is important for the repair of double strand breaks in eukaryotes but not prokaryotes. NHEJ requires the Rad51 protein, a eukaryotic homolog of RecA. NHEJ is important for generating antibody diversity in higher eukaryotes. NHEJ requires RecBCD in order to generate single stranded 3’ tails. In NHEJ, the LigD protein recognizes and binds to double strand breaks.

2.

Which of the following proteins participates in homologous recombination in E. coli? A. B. C. D. E. (D) LigD DNA polymerase IV Artemis RuvB Ku

3.

Which of the following statements is NOT correct? A. B. C. D. E. (C) RecA is absolutely required for homologous recombination in E. coli. RecA binds to single stranded DNA. RecA preferentially degrades one strand of DNA in order to generate a 3’ tail. RecA catalyzes strand invasion. RecA does not directly participate in the resolution of Holliday junctions.

4.

Which of the following statements concerning homologous recombination in E. coli is correct? A. B. C. D. E. (B) RuvC catalyzes branch migration of Holliday junctions. DNA replication is required in homologous recombination. Chi sites are 8 nucleotide sequences found approximately once in every 65kb of E. coli chromosomal DNA. When RecBCD encounters a chi site, it stops degrading the strand with a 5’ end. Thymine dimers cannot be repaired by homologous recombination.

5.

A given prokaryotic protein-coding gene exhibits all of the following characteristics EXCEPT: A. B. C. D. E. (A) Codes for only a single translational start site. Occupies an open reading frame (ORFs). Is oriented in one direction or the other, but not both on the replicon. Generally is read in a single reading frame. Is composed of a run...