b****o
发帖数: 169 | 1 Two strains of bacteria are grown together in culture. One strain is
resistant to ampicillin and the other to gentamicin; but after coculture,
colonies are produced that are resistant to both antibiotics. in a parallel
experiment, the cell-free supernatant liquid of the cocultured bacteria is
treated with DNAse and then added to cultures. In this case, no colonies
grow on medium containing both antibiotics. Which of the following processes
best explains theres observations?
A.Conjugation
B.Mut | a*****s
发帖数: 838 | 2 I think the parallel experiment is just to tell you that the choice of "tran
sformation" is eliminated. So it seems likely through either conjugation or
transduction. Seems both gentamicin and ampicillin resistance are carried by
plasmids,
so I guess it's conjugation? What's the answer?
parallel
is
processes
【在 b****o 的大作中提到】
: Two strains of bacteria are grown together in culture. One strain is
: resistant to ampicillin and the other to gentamicin; but after coculture,
: colonies are produced that are resistant to both antibiotics. in a parallel
: experiment, the cell-free supernatant liquid of the cocultured bacteria is
: treated with DNAse and then added to cultures. In this case, no colonies
: grow on medium containing both antibiotics. Which of the following processes
: best explains theres observations?
: A.Conjugation
: B.Mut
| b****o
发帖数: 169 | 3 the answer is D, transformation. This is why I am confused.
Here is its explanation: When new genetic traits are acquired by strains of
bacteria following addition of cell-free, DNAse-treted supernates, it
implies that peices of DNA have been picked up by the living cells, and
incoporated into their chromosomes. This is the definition of transformation.
Looks like it is conflicting to the answer. in the question stem, it says
the resistance is not acquired. if this is true, then why did transfor
【在 a*****s 的大作中提到】
: I think the parallel experiment is just to tell you that the choice of "tran
: sformation" is eliminated. So it seems likely through either conjugation or
: transduction. Seems both gentamicin and ampicillin resistance are carried by
: plasmids,
: so I guess it's conjugation? What's the answer?
:
: parallel
: is
: processes
| s******n
发帖数: 2279 | 4 hehe, I got it right
since DNAase destroy any potential DNA released from the dying/dead bacteria
, that's why it prevent the gene transfer
if through other ways, it won't be affected by removal of floating DNA. | a*****s
发帖数: 838 | 5 I see.. now it seems transformation is the right answer. I read the question
and thought too much :( Thats why I ended up with excluding the most likely
answer first and over analyzed a lot of things.
The transformation happened in the first experiment; the parallel is to tell
you that when the DNA fragments are digested, (therefore no source for tran
sformation), no resistance observed. To answer your question, yes DNase dige
st DNA away. In the parallel experiment, DNA fragments gone, so no tr
【在 b****o 的大作中提到】
: the answer is D, transformation. This is why I am confused.
: Here is its explanation: When new genetic traits are acquired by strains of
: bacteria following addition of cell-free, DNAse-treted supernates, it
: implies that peices of DNA have been picked up by the living cells, and
: incoporated into their chromosomes. This is the definition of transformation.
: Looks like it is conflicting to the answer. in the question stem, it says
: the resistance is not acquired. if this is true, then why did transfor
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