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| 1 | |
An episome consisting of a conjugative plasmid containing chromosomal DNA from an imprecise excision is a(n):
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| | A) | transposable element |
| | B) | Hfr strain |
| | C) | plasmid |
| | D) | transducing phage |
| | E) | F' |
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| 2 | |
Sequential transfer of chromosomal genes is carried out by a(n):
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| | A) | transposable element |
| | B) | Hfr strain |
| | C) | plasmid |
| | D) | transducing phage |
| | E) | F' |
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| 3 | |
Packaging of chromosomal DNA into a virus produces a(n):
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| | A) | transposable element |
| | B) | Hfr strain |
| | C) | plasmid |
| | D) | transducing phage |
| | E) | F' |
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| 4 | |
An autonomous element that can move itself within cells but not between cells is a(n):
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| | A) | transposable element |
| | B) | Hfr strain |
| | C) | plasmid |
| | D) | transducing phage |
| | E) | F' |
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| 5 | |
A 100 kb circular DNA molecule with an origin of replication is an example of a(n):
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| | A) | transposable element |
| | B) | Hfr strain |
| | C) | plasmid |
| | D) | transducing phage |
| | E) | F' |
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| 6 | |
Isolation of bacteria resistant to penicillin would be considered a ________, while isolation of bacteria able to utilize lactose as a carbon source is a ________.
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| | A) | screen; selection |
| | B) | selection; screen |
| | C) | transformation; conjugation |
| | D) | conjugation; transformation |
| | E) | transduction; conjugation |
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| 7 | |
A strain of E. coli is trp- his- lac+. Which medium would this bacterium grow on?
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| | A) | lactose + histidine + tryptophan |
| | B) | glucose + histidine - tryptophan |
| | C) | maltose - histidine + tryptophan |
| | D) | glucose, - histidine, - tryptophan |
| | E) | b and c |
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| 8 | |
How many crossover events are needed to integrate an entire plasmid into a circular bacterial chromosome?
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| | A) | one |
| | B) | two |
| | C) | three |
| | D) | four |
| | E) | five |
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| 9 | |
Streptomycin resistant (Strr) cells are plated on medium with 25 µg/ml gentimycin. All bacteria grow. What is the most likely explanation?
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| | A) | new mutations have arisen |
| | B) | streptomycin resistance was acquired by a multiple drug resistance element |
| | C) | cells have now lost streptomycin resistance |
| | D) | cells have undergone conjugation |
| | E) | none of the above. |
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| 10 | |
E. coli DNA introduced into S. typhimurium occasionally undergoes recombination, but this is very rare. Which of the following might increase recombination?
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| | A) | propagate E. coli genes on plasmids in S. typhimurium first |
| | B) | knock out E. coli restriction/modification system |
| | C) | knock out S. typhimurium restriction/modification system |
| | D) | a & c |
| | E) | all of these would increase recombination |
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| 11 | |
Two genes are found to be two minutes apart by mating and co-transduce about 10% of the time with phage P1. A plasmid with an insertion sequence in it is introduced, and after many generations the two genes no longer co-transduce at any frequency. What has most likely occurred?
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| | A) | the insertion sequence has inserted between the genes |
| | B) | accumulated point mutations prevent recombination in the recipient |
| | C) | duplication of intervening genes has separated the markers |
| | D) | a & b |
| | E) | none of the above |
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| 12 | |
There are 'promiscuous plasmids,' plasmids that can be interchanged between very different bacteria. What properties would such plasmids have?
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| | A) | replication origin that functions in different cells |
| | B) | plasmid must escape restriction/modification systems |
| | C) | plasmid must carry chromosomal genes |
| | D) | b & c |
| | E) | a & b |
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| 13 | |
Resistance to streptomycin occurs about once in 109 cells in E. coli. Resistance to penicillin occurs about once in 108. Resistance to gentimycin occurs about once in 109. Using several sequential rounds of selection without mutagenesis, what are the chances of eventually isolating a triply resistant bacterium?
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| | A) | nearly certain |
| | B) | One in 10M9 |
| | C) | One in 1026 |
| | D) | One in 10648 |
| | E) | nearly impossible |
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| 14 | |
A plasmid containing a region of wild-type DNA is introduced into a wild-type bacterium. This organism is properly termed a:
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| | A) | exconjugant |
| | B) | lysogen |
| | C) | transductant |
| | D) | heterogenote |
| | E) | merozygote |
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| 15 | |
An att- lambda phage lysogen carrying the wild-type gal operon in a gal- recipient is properly termed a:
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| | A) | exconjugant |
| | B) | knockout |
| | C) | transformant |
| | D) | heterogenote |
| | E) | merozygote |
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| 16 | |
A transposon inserts into an operon. What are the likely consequences?
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| | A) | all genes are knocked out |
| | B) | downstream genes are knocked out |
| | C) | flanking genes cotransduce less |
| | D) | a & c |
| | E) | b & c |
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| 17 | |
Tn10 is introduced into wild type E. coli in an effort to find mutants unable to use lactose. You would first plate the cells on minimal salts medium with:
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| | A) | tetracycline |
| | B) | tetracycline + lactose |
| | C) | tetracycline + glucose |
| | D) | lactose |
| | E) | glucose |
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| 18 | |
Following the previous experiment, you would screen cells by replica plating colonies on minimal salt medium with:
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| | A) | tetracycline |
| | B) | tetracycline + lactose |
| | C) | tetracycline + glucose |
| | D) | lactose |
| | E) | glucose |
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| 19 | |
(Questions 19 and 20)
You conduct matings with two different Hfr strains and obtain the following data:
| % exconjugants carrying marker from | | marker | Hfr1 | Hfr2 | |
A |
0 |
78 | |
B |
50 |
0 | |
C |
73 |
0 | |
D |
48 |
93 | |
E |
0 |
69 | |
F |
81 |
0 | |
G |
90 |
0 |
What is the order of these markers?
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| | A) | DGFACEB |
| | B) | DAEGFCB |
| | C) | GFCBDEA |
| | D) | BECAFGD |
| | E) | CBDAEFG |
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| 20 | |
Which genes appear to be most tightly linked?
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| | A) | D & B |
| | B) | F & A |
| | C) | G & D |
| | D) | E & A |
| | E) | G & F |
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| 21 | |
(Questions 21 and 22)
You perform a generalized transduction mapping experiment by growing phage on a wild-type host and transducing a recipient that is mutant for three genes. The results are shown in the table below:
| phenotype | number
of transductants | |
F+M-R- |
116 | |
F+M+R- |
447 | |
F+M-R+ |
7 | |
F-M+R+ |
490 |
What is the order of the genes?
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| | A) | RFM |
| | B) | MRF |
| | C) | FMR |
| | D) | a or b |
| | E) | b or c |
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| 22 | |
Is M closer to F or R?
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| | A) | F |
| | B) | R |
| | C) | equidistant |
| | D) | can't tell |
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| 23 | |
Order the following steps in the generation and mapping of an auxotrophic mutant in E. coli:
A. Screen for auxotrophy
B. Selection for antibiotic resistance
C. Sequence DNA and match to genomic sequence database
D. Use PCR to amplify transposon sequence and adjacent DNA
E. Transposon mutagenesis
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| | A) | EBADC |
| | B) | AEBCD |
| | C) | EABDC |
| | D) | BAECD |
| | E) | AEBDC |
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| 24 | |
A generalized transducing phage is used to transduce an a-b-c-d-e-f- recipient strain of E. coli with an a+b+c+d+e+f+ donor. The recipient culture is plated on various media with the results shown in the table below. (Note that "a-" indicates a requirement for A as a nutrient, etc.).
| Compounds added to minimal medium | Presence (+) or absence (-) of colonies | |
ABCF |
- | |
ABDF |
+ | |
ABEF |
- | |
ACDF |
- | |
ACEF |
- | |
ADEF |
- | |
ABCE |
+ | |
BCDF |
+ | |
BCEF |
+ | |
BDEF |
- |
What is the order of the genes?
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| | A) | DECBAF |
| | B) | ABCDEF |
| | C) | DEBFAC |
| | D) | BACDEF |
| | E) | FDAECB |
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| 25 | |
You make the following E. coli cross: Hfr E1-his+strs X F- E2-his-strr, in which str determines resistance or sensitivity to streptomycin, his determines histidine requirement for growth, and E1 and E2 are two very close sites within the trpE gene that result in an inability to use tryptophan as an energy source. The three genes are in the order: trpE-his-str. After about an hour, the mixture is plated on a medium containing streptomycin, with glucose as the energy source. Many of the his+ colonies that grow are found to be capable of using tryptophan. However, hardly any of the his+ colonies from the reciprocal cross Hfr E2-his-strr X F-E1-his+strs are found to be capable of using tryptophan as an energy source. What is the order of the E1 and E2 sites in relation to the his locus?
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| | A) | E1 - E2 - his |
| | B) | E2 - E1 - his |
| | C) | E1 - his - E2 |
| | D) | can't tell |
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