what is co transformation scientificaly ? - what is co transformation scientificaly ? (Mar/16/2009 )

Everybody Hi ,
Actually my experiment was cotransformation for Top10 , but my Professor told me i have to prepare a competent cell harboring one plasmid then i have to do a single transformation, here i got much more clones in plate than in cotransformation .
Can anybody tell me what is the scientific reason for the difference in enumerated clones betwwen them ?
Thank you
Dawood

Presuming that what you have been told to do is either
1) Transform both plasmids at once
or
2) Transform the plasmids one after the other

And the question is why is there a higher number of clones produced when transforming the second plasmid for (2) above.

The answer is that if you try and transform and have different selective markers on each plasmid (e.g. ampicillin on one and kanamycin on the other), the number of bacteria that will take up both is limited. However, if you do them sequentially as in (2), "all" the bacteria being transformed already have the first plasmid there, so it is just like transforming one plasmid.