docarchana
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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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| young_doc
Forum Guru
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D. Transformation. (i.e. bacteria pick-up genetic material from the medium)
This sounds A LOT like a QBank question....and i don't remember seeing it in N3??? Interesting..
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| elias
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agree
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| drmike11
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agree as well.
transformation is when bacteria can pick of free DNA - DNase degrades free DNA and therefore, the bacteria will not be able to use it.
conjugation and transduction require direct bacteria-to-bacteria and virus contact, respectively, so they would not be affected by the DNase (since the question tells us to assume the cells are impermeable to DNase).
transposition also occurs within a cell, these are the jumping genes. these genes can jump from one chromosome to another location in the same ch or another ch, or a plasmid - but not other cells. the cell is impermeable to DNase so this would not be affected either
mutation occurs too random to account for such a dramatic change, and even if it could, this occurs within the cell, which is again, is impermeable to the DNase
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| lq2006
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D. Transformation
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| SmokyWaters
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wud be transformation as DNAse clears all the free DNA so
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