>myersm at rockvax.rockefeller.edu
I used a vector similar to Casper, and I had very low efficiency in cloning
fragments larger than ~10 kb. In some cases constructs rearranged. I found
out that, the P-element flanks used in the vector were taken from its
insertion into white gene. Since the vector contains also white gene, these
sequences (~200 and ~400bp) are repeated and may enable intramollecular
recombination, which I could observe. I used E.coli DH5-alfa. You may
check Casper's sequence, whether it contains direct repeats. Slawek.