probes for slot or northern blot - help!! (Oct/19/2005 )

Hi. I'm starting northern or dot blotting to see the expression pattern, but from the very first step, I'm stuck!!

Probe design is not easy for me. Please help!!

1. Is oligo probe (5' 32P labelled 35bp) specific and working well??

2. Does the probes produced by PCR or primer extension (Klenow) work well? How long should they be?

3. Which one (oligo or ds DNA) do you prefer? Or do you prefer other types of probe (ss DNA, RNA)?

Thanks in advance for your kindness.

For Northern blot, I use PCR to amplify my probes and use Klenow enzyme to label P32-dCTP into my probes (not end labeling). I always use dsDNA.

hi
for northern :
acrylamide northerns (ie small RNA) : oligos, end labelling dATP P32
formaldehyde/agarose gel : cDNA, klenow labelling, dCTP P32

Thanks a lot!!