Question on basic cloning theory

rocky rockyho at
Wed May 2 11:05:49 EST 2001

On Wed, 02 May 2001 10:56:52 +0100, Simon Andrews
<simon.andrews at> wrote:

>rocky wrote:
>> Hi
>> Can anyone tell me:
>> Is there only one plasmid goes into single competent cell?
>Not necessarily.
>> If no, how can I make sure I get a unique clone from the single
>> bacterial colony?
>Bacteria have inbuilt mechanisms for regulating the copy number of a
>particular plasmid they carry.  (Look for information on partitioning
>systems).  ......
>It is possible that the larger product is toxic (maybe only mildly) to
>the cell so there is an evolutionary pressure to delete part of this. 
>We have had clones which were unstable for this reason, and gave bands
>of varying size when prepped.  Try using a vector with transcriptional
>control if this might be a problem.

Thanks for information

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