小中大1. If you use the same template, but it has been thawed and frozen repeatedly,
you may have problem.
2. Are you sure you use the completely identical components including water?
3. Do you use the same tube, once one of my frend changed his Eppendorf tube, but
he failed, cause some tubes may have DNase?
4. Do you do normal PCR or real-time PCR, if normal PCR, how do you check result?
Normally people use agarose gel, so also check if you TAE or TBE buffer works well,
or prepare new buffer.
5. Have you check if you enzyme still works? Do you make positive control every time
which makes sure that your whole system works!
6.Check your machine once agian
Hope it is useful for you
