Recently I've been doing some PCRs and the primes used to work a month ago, but now that we want to repeat the experiment, they are not working anymore. I have noticed something in my gels, and it is that I dye them with ethidium bromide and then wash the excess with distilled water. When I reveal the gel in the transilluminator the DNA seems to faint until it disappears. I immerse the gel in the EtBr solution again but to no avail, it's like the DNA is leaving the gel somehow. Anyone knows wats going on?
Hi Gabriel Salazar Robles if you leave the gel on the transilluminator for too long then photobleaching of DNA can occur causing the EtBr fluorescence to weaken and eventually disappear. If this happens then best to take a picture of the gel as quickly as possible. Since you successfully did this a month ago and nothing else has changed, wear and tear of the UV filter in the transilluminator could be the issue. Check with others and see if they also have this issue.
As Leonard Koolman says photobleaching is likely and depends on the time that the gel spends under UV light and the state of the UV bulbs and the filter. One indicator that the bulbs are failing or that the filter is allowing too much short wavelength UV light through is that you start to see the bulbs in your imaging of the gel
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