vallia
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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
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D?
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| ashfaque
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answer is A conjugation as enviroment contain DNAses so transformation is not possible
Edited by new_n_lost on 08/05/07 - 06:13 PM
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| cuadrado_g
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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
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definetly D
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| laura81
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why not A?
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| babydoc4usmle
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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
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so its A
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| babydoc4usmle
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???? 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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