Primer extension

[lumdicks]

Hi,

      I've encountered some problems in performing primer extension. It
is that I only get smear in the X-ray film instead of the band. So, what
is the problem of this?? Besides, is the salt in the extension reaction
affect gel electrophoresis?? Because my sequencing gel run very strange
and I suspect the problem is due to the excessive salt in the reaction.

Thanks in advance.

Regards,
Lum