polytene chromosome in situs

[Gretchen Kaiser]

i am trying to map a P-element using a probe that is about 7kb long and
am having, uh, difficulty.  i am using DETEK Alk (an AP signal
generating system that uses BCIP and NBT) to detect a biotinylated probe
because i was told that it was more sensitive than DAB.  does anyone
have any opinion on this?  the former worked for another P-element that
i was mapping (so i don't think that it is the rpotocol that i am using)
but the probe was bigger...
any suggestions about dealing with small probes?

thanks....
glkaiser at princeton.edu