Simple question that is hard to answer

Tim Fitzwater via (by tfitzwater from
Thu Feb 22 11:53:11 EST 2007

I studied plasmid copy number control (ColE 1) for 12 years, and since then have been cloning SELEX pools for the past 13 years.  
When you have two clones co-transformed into the same cell (same insert, same vector, same antibiotic resistance) they cannot co-exist in the same cell.  This is true even for high copy number pUC origin plasmids.  
SELEX pools containing an evolved 40 bp random region can contain distinct sequences or vary by 1 or more basepairs.  During the generations required to grow a colony and grow the first liquid culture prior to plasmid prep and sequencing, segregation occurs and most preps will contain a single sequence.  

Tim Fitzwater

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