Weird kinased oligo pattern...

[G K L Munro]

I have been having some trouble with oligos which I am using for PCR and 
sequencing.   Finally last week I kinased them up to have a look (Iknow,  I 
should have done it straight away!).   Anyway,  although there is a reasonably
sized band at the right size for the oligo,  there are ladders extending in
each direction!!!   The oligos are 19mer,  22mer and a 25mer.   They were
kinased and run on a 20%acrylamide/7M Urea gel at 50C.   I have never seen a 
ladder extending in the n+1 direction before.   How does this happen?

Gordon