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vallia
Forum Guru Topics: 96 Posts: 884 |
12. Bacterial strain X is resistant to ampicillin and sensitive to gentamicin. Bacterial strain Y is resistant to gentamicin and sensitive to ampicillin. Bacterial strains X and Y are grown in mixed culture in medium without antibiotics, then the culture is plated on medium containing both ampicillin and gentamicin. Bacterial colonies grow on the plates. In a second experiment, DNase is added to the mixed culture medium. When this mixed culture is plated on medium containing both antibiotics, no colonies grow. Assuming that bacterial cells are impermeable to DNase, which of the following processes best explains these observations? A. Conjugation B. Mutation C. Transduction D. Transformation E. Transposition
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fox
| Forum Guru  Topics: 70 Posts: 720
D?
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ashfaque
| Forum Senior Topics: 0 Posts: 139
answer is A conjugation as enviroment contain DNAses so transformation is not possible Edited by new_n_lost on Aug 05, 2007 - 4:13 PM
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cuadrado_g
| Forum Senior Topics: 16 Posts: 152
From the options, only A,C,and D makes some sense for me. From them conjugation would not be affected in a DNAase media bcause there is genetic material transfered using a pili. Transduction means transfering material with a phage and it would not be affected with the DNAase since they are encapsulated. Transformation means incorporation of free DNA from the extracelular compartment into the bacterial cromosome, and this free DNA could be destroyed in a DNAase media, explaining the observation of the second experiment; so I think that the correct answer is D.
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smal
| Forum Guru  Topics: 141 Posts: 723
definetly D
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laura81
| Forum Elite Topics: 34 Posts: 183
why not A?
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babydoc4usmle
| Forum Guru  Topics: 18 Posts: 627
transformation is a process that requires free DNA floating around in medium so bugs can pick it up and aquire new genes/info having DNase in medium makes it impossibe conjuation is not affected by medium content - two bugs give information directly one another
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laura81
| Forum Elite Topics: 34 Posts: 183
so its A
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babydoc4usmle
| Forum Guru Topics: 18 Posts: 627
???? conjuation is not affected by medium content - two bugs give information directly one another if you have bug A and bug B conjugate - you'll have genetic information exchange REGARDLESS of presence of DNas in medium and in this case you'll have growth in both cases but there is NO GROWTH in DNase presence IT CAN NOT BE CONJUGATION
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