MadSci Network: Molecular Biology

Re: Does plasmid size affect transformation efficiency? How significant is it?

Date: Mon Nov 27 21:59:32 2000
Posted By: Evelyn Tsang, Research Assistant
Area of science: Molecular Biology
ID: 974752536.Mb

Hello Timothy!

Wow, what an interesting experiment!  Plasmid size, or rather the size of 
the insert, does affect transformation rate.  From what I have read, the 
size of the insert is inversely proportional to the efficiency of ligation 
and transformation. The magic number is around 15kb for the insert.  Any 
foreign DNA larger than that and the plasmid may "spontaneously lose the 

Just to put things in perspective, the protocols for nested deletions that 
I found gave recipes for inserts around 2kb.  So, if you start off with a 
fragment the size of 15kb and create nested deletions down to several 
100bp, you should see quite a change in transformation efficiency :)

Best of luck and I hope to hear about your results!


My references:
1. Griffiths, et al., "Ch.14, Recombinant DNA Technology" from "Genetic 
Analysis 6th ed."

2. Zubay et al., "Ch. 27, DNA Manipulation and its Applications" 
from "Biochemistry, vol.3" 

3. Slatko, B, Heinrich, P, Nixon, BT and Voytas, D. (Contributors in)"Ch. 
7.2, Constructin Nested Deletions for Use in DNA Sequencing" from "Short 
Protocols in Molecular Biology"

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