I ran a PCR product of ~300 bp on a 2% TAE-agarose gel for 30 minutes. I used Sybr-safe as a DNA stain. Voltage was 80V.
When I imaged the gel, the DNA on the bottom half of the gel, including the ladder had disappeared (it showed no bands). The DNA in the top half looked-clear and well-separated, but the bands on the bottom were somehow missing.
What could be the reason? I've never encountered this before.
I know it's not due to gel overheating - I ran the gel in the cold room and when it was done it was cold to the touch.