Simple question that is hard to answer

Peter Ellis via (by pjie2 from
Fri Feb 16 15:27:14 EST 2007

peter wrote:
> Duncan,
> Your input is always appreciated, just my question was different and I
> don't know how better to describe  - can one have two alleles of the
> SAME Plasmid in the SAME cell, not different ori, not different
> antibiotic resistances, everything is the same, just point muataion
> that comes from cloning of heteroduplex DNA that has a mutation.
> Peter

It would seem unlikely.  Even assuming the heteroduplex molecule got cloned 
in the first place, my suspicion is that the first time it gets replicated, 
the mismatch would be "corrected" and you'd get two identical daughter 
copies of one allele or the other.

Conversely, assuming you're transforming a mixed population of alleles in 
the first place, it's very unlikely that you'll get both alleles in the same 
bacterium - the whole *point* of the transformation is that you only get one 
plasmid into any given bacterium.

You might end up with a heterogeneous population of plasmids inside the same 
bacterium, but that'll only happen if it's (a) a high copy number plasmid 
and (b) acquired the mutation within the bacterium.


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