migration of dyes and DNA thru alkaline agarose gels

[Sharon]

Dear Experts,

I need to run an alkaline agarose gel to crudely measure the length 
of a primer extension reaction (prior to doing a urea gel to closely 
and accurately measure length).  Does anyone know what the migration 
of bromophenol blue and xylene cyanol are in alkaline agarose gels 
relative to DNA size (or alkaline polyacrylamide gels)?

Thanks,
Sharon