Genetics Test 3 Ch. 6 Flashcards
1) Which of the following is false regarding plasmids? <br></br>A) They can have genes that promote their own transfer from one bacterium to another.<br></br>B) They contain essential genes for metabolism.<br></br>C) They can carry genes for antibiotic resistance.<br></br>D) They generally replicate autonomously.<br></br>E) They are small double stranded circular DNA molecules.
Answer: B
2) Which of the following is true of a bacterial strain that is his+ lac+ gal- ampR. <br></br>A) It is unable to synthesize histidine.<br></br>B) It is auxotrophic for histidine.<br></br>C) It is unable to break down lactose.<br></br>D) It will grow on ampicillin.<br></br>E) It can use galactose as an energy source.
Answer: D
3) Which of the following is incorrect about genetic analysis and mapping in bacteria and bacteriophages?<br></br>A) Generalized transduction uses lytic phage and specialized transduction uses a lysogenic phage.<br></br>B) Conjugation, transformation, and transduction all require recombination.<br></br>C) Conjugation requires cell- to- cell contact.<br></br>D) Conjugation, transformation, and transduction can all be used to map the order of genes on a bacterial chromosome.<br></br>E) Transformation requires a vector to carry donor DNA fragments to the recipient cell.
Answer: E
4) Why does conjugation with an Hfr donor result in a much higher rate of gene transfer than conjugation with an F+ donor?<br></br>A) An F+ donor makes fewer pili.<br></br>B) The Hfr donor segment must undergo recombination in the recipient.<br></br>C) An F+ donor’s T strand is slow to reach the pilus.<br></br>D) The Hfr donor transfers genes from the chromosome and not the plasmid.<br></br>E) The F+ donor segment must undergo recombination in the recipient.
Answer: D
6) Which of the following is NOT a step involved in rolling circle replication during conjugation? <br></br>A) A protein complex known as the relaxosome cuts one strand of the F+ plasmid.<br></br>B) A double stranded plasmid is transferred to the F- cell through the conjugation pilus.<br></br>C) Rolling circle replication occurs in the donor.<br></br>D) Replication begins at the oriT after relaxosome binding.<br></br>E) Relaxase facilitates passage of the T strand into the recipient cell.
Answer: B
7) When F+ conjugation occurs successfully, only one copy of the F plasmid single- stranded DNA is transferred. What else must minimally occur?<br></br>A) circularization plus replication of the new recipient DNA<br></br> B) circularization of the recipient’s new DNA<br></br>C) rolling circle replication in the recipient cell<br></br>D) continuation of rolling circle replication in the donor cell and replication in the recipient cell <br></br>E) stopping the rolling circle replication after one copy length, circularization, and replication
Answer: E
8) Which of the following is an accurate statement regarding F factor states? <br></br>A) F+ and Hfr cells cannot convert exconjugants to a donor state.<br></br>B) F+ and F’ cells cannot transfer donor genes to exconjugants.<br></br>C) An F+ cell can convert exconjugants to a donor state, as well as change their genotype.<br></br>D) An F’ cell can convert exconjugants to a donor state, as well as change their genotype.<br></br>E) An Hfr cell can convert exconjugants to a donor state, as well as change their genotype.
Answer: D
9) To map genes of a bacterial strain, conjugation must be interrupted at given times. Suppose you have Hfr cells of genotype a+b+c+d+e+strR and F- cells of genotype a- b- c- d- e- strS and you combine these two cultures in liquid medium in four blenders at time 0. After intervals of 3, 6, 9, and 12 minutes, you turn on successive blenders. What role does the blender play in the experiment?<br></br>A) shears the sex pili of conjugants<br></br> <br></br>B) serves as a culture container only<br></br>C) acts as a mechanism to bring cells into contact<br></br>D) hastens conjugation events<br></br>E) speeds up molecular movement of DNA
Answer: A
10) To map genes of a bacterial strain, conjugation must be interrupted at given times. Suppose you have Hfr cells of genotype a+b+c+d+e+strR and F- cells of genotype a- b- c- d- e- strS and you combine these two cultures in liquid medium in four blenders at time 0. After intervals of 3, 6, 9, and 12 minutes, you turn on successive blenders. The resulting cultures were then plated on medium containing streptomycin. Why?<br></br>A) to eliminate non- conjugating Hfr cells<br></br>B) to selectively eliminate cells that have taken in F+ genes<br></br>C) to eliminate non- conjugated F- cells<br></br>D) to eliminate all non- conjugated cells
Answer: C
11) Which of the following allows the compilation of time- of- entry maps? 13)<br></br>A) the recognition of phenotype interaction<br></br>B) the fact that gene entry can proceed in either direction<br></br>C) the use of many replicates of each experiment<br></br>D) the observation that Hfr genes recombine so efficiently E) the use of appropriate controls repeatedly
Answer: B
12) In five Hfr strains, each of which was used to build a time- of- entry map, the genes entered the recipient cells as follows:<br></br>Strain 1: S L A C T F<br></br>Strain 2: N P F T C A Strain 3: T F P N U Y<br></br>Strain 4: S H Y U N P<br></br>Strain 5: U N P F T C<br></br>Which of the following represents a correct compilation of these results<br></br>A) N P F T S L A C H U T<br></br> <br></br>B) T C A L S P N U Y H<br></br>C) S L A C T F P N U Y H<br></br>D) S L A C T F P N H C U<br></br>E) U N P F T C A L S T F
Answer: C
13) An Fȝ donor includes F DNA plus a segment of bacterial chromosome DNA. If conjugation is interrupted before the entire Fȝ chromosome transfers, what could be the expected consequences?<br></br>A) a smaller Fȝ plasmid than had been present in the donor<br></br> <br></br>B) change of the recipient from F- to F+<br></br>C) formation of a recipient that is a stable partial diploid<br></br>D) integration of some but not all Fȝ genes into the recipient’s chromosome E) failure of the Fȝ strand to circularize in the recipient
Answer: E
14) Which of the following is NOT a step in transformation?<br></br>A) Donor cell DNA binds to a receptor site on the recipient cell.<br></br>B) DNA fragments pair with homologous regions of the recipient cell chromosome.<br></br>C) The donor cell lyses, releasing pieces of its chromosome into the environment.<br></br>D) DNA recombines with the recipient cell chromosome.<br></br>E) Both strands of the donor cell DNA are degraded.
Answer: E
15) A competent bacterial strain with genes a, b, and c is transformed by a donor bacterial fragment.Cotransformation frequencies for each gene pair are as follows:<br></br>a and b 0.04% a and c 0.02% b and c 0.0064%<br></br>Which conclusion can be definitively made from this data?<br></br>A) Cotransformation of b and c is so frequent, they must be one gene.<br></br>B) Gene b is closer to c than to a. <br></br>C) Gene a is closer to c than to b.<br></br>D) Gene order is a, b, then c.<br></br>E) Genes b and c are farthest apart.
Answer: E
16) Which of the following statements about the T4 lytic life cycle is false? <br></br>A) Under the direction of phage genes, transcription and translation produce new phage components.<br></br> <br></br>B) The phage DNA is injected into the host.<br></br>C) Progeny phage particles are released by lysis from host bacteria.<br></br>D) The phage DNA is integrated into the host chromosome.<br></br>E) The host DNA breaks down.
Answer: D
