DNA disappearing after restriction - (Sep/03/2014 )

I agree that your gel shows either primer-dimers or excess primer, and a strong band, which is probably your desired product. The DNA is there after your PCR, so you simply need to find out what has happened to it. Here's some suggestions:

1. Mix your RE digest and instead of heating it, load it directly on a gel.

2. Mix your RE digest, but omit the TaqI enzyme. Heat as normal

3. Mix your RE digest, but omit the heating at 80.

4. Mix your RE digest, but instead of buffer or enzyme, dilute with the same amounts of water (no heating)

Load all of these, together with your normal RE digest (with heating at 80) on a gel and show us the results.