Questions on creating stable transfectants

[Student]

Dear All,

I have come round to doing my first stable transfection experiment and have
the following questions and wonder if anyone can help:

1) Can anyone provide any reference for the theory of stable transfection? I
only know that the DNA goes into the nucleus and integrates somehow into the
host chromosome but not much details. It would be nice to know how it does
that and where the DNA actually goes. Can one control where it integrates?,
etc.

2) I did some COS-7 transfection before and I am wondering why can't COS-7
be used for stable transfection? Has it got to do with the high copy number
of the plasmids for COS-7 transfection which becomes lethal to the cell?

3) When I did my first stable experiment, I picked cell foci (CHO; after
selection with Geneticin and media lacking ribo/deoxyribunucleosides) with
forceps and sterilised filter paper squares immersed with trypsin/EDTA. I
found this quite fiddly and I 've also introduced some infections into some
wells.Can anyone suggest a neater and cleaner way of picking these foci?

Many thanks for any insight.