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17 Cards in this Set
- Front
- Back
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What about the transfer region of R100 is similar to F plasmid?
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- they both have tra operon & oriT which allow them to be transferred from the donor to recipient
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R100 is most likely a hybrid of what two types of plasmids?
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- one with drug resistance & one with transfer plasmid (similar to F)
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If cell contains both R100 & F factor do they transfer at a high or low frequency?
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- low frequency
- can use R100 as sex pilus similar to how F factor does |
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R-factors often carry their drug resistance genes as parts of ____________. This means they can jump to different DNA molecules in the same cell.
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- transposable elements.
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what is a consequence of replicative transposition?
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- drug resistance can move from one plasmid to another
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What are the 3 categories of transposable elements?
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1) IS elements
2) simple transposons 3) composite (complex) transposons |
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______ are the simplest transposable elements
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- IS elements
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What are the 2 features of the IS elements (simplest transposable elements)?
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1) inverted repeats at either side of DNA
2) transposase - protein that mediates transposition & represses own transcription |
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How does the transposase gene regulate itself?
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- as transposase conc increaes it blocks further transcription of it's gene
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What happens at the target side where tranposon or IS element lands? What is important that happens to the target site?
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1) target site cut staggered
2) transposon ligated into the cut target 3) gaps are filled by DNA polymerase - the target site is duplicated! |
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Whats makes up composite transposable elements?
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- other genes flanked by IS sequences
- each individual IS sequence can transpose, the whole thing can also transpose |
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TN3 is a _____ transposon. Why are they simple? What genes are there?
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- simple
- because repeats at their ends & sequences inbetween required for transposition & can also have drug resistance - have TnpA = transposase, TnpR = resolvase, drug resistance |
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What are the 3 streps of replicative transposition?
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1) copying the Tn
2) cointegrate formation (the plasmids together) 3) resolution to leave behind copy of Tn at new site (gives rise to original plasmid & new plasmid w/ transposon) |
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_____ or ____ can resolve the cointegrate. Which is faster & more efficient?
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- TnpR (resolvase)
- RecA - TnpR is quicker & dedicated to this - RecA is slower |
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What is the function of TnpR besides resolviase?
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- repressor of TnpA (transposase) synthesis
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If cointegrate is present long enough what can happen during conjugation?
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- the whole thing can transfer meaning that all of the drug resistance will transfer to the bacterial chromosome
- or if conintegrate resolves drug resistnace can be transferred to the conjugable plasmid & transfer of all the drug resistance can occur |
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What allows non-conjugable plasmid to be transferred via conjugation?
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- the presence of another conjugative plasmid in the cell that can form cointegrate & transfer the whole thing
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