DNA integration after transfection of mammalian cells

[Ian Lyons]

DNA injected into fertilised mouse eggs does not seem to integrate 
until the four to 16 cell stage.  This means that at the blastocyst
stage, almost all injected pronuclear eggs have developed to 
chimaeras.  That only a small number of Inner Cell Mass cells 
go on to form the embryo proper is probably what reduces the 
proportion of chimaeric live young to the numbers we see.  
It's sort of a cellular founder effect.  

Is this the case for cultured cells?  Do only a proportion 
of the daughter cells of a transfected cell get transformed?  
In most experiments in which we apply selection immediately 
after transfection we only see the progeny of cells which 
integrated the DNA.  

Does integration occur immediately, or 0 to 3 cell divisions
after DNA introduction?

Facts or theory welcome!

Any suggestions as to the best microinjection device to do 
this experiment with?  Do Eppendorf still make a microinjector 
driven by compressed gas?

Thanks for any input

IAN LYONS
Biochem, Adelaide
AUSTRALIA