There is a rule on StackOverflow: If your code turns out to not have been working as expected simply because you misspelled a variable somewhere, the question is considered off-topic.

This is a reasonable rule: Indeed, how is such a question useful to anyone but the author? It is unlikely that anyone who comes from a search for "I tried to do X but couldn't, why?" will happen to have made the same mistake.

In this question the user is asking why their DNA bands are too faint. It turns out that the problem is that they used the wrong illuminator - a blue LED meant for CYBR Green, not a UV for EtBr.

I don't believe this question would be useful to other people who come trying to figure out how to make their bands brighter. In my answer, I've listed several reasons for faint bands, note how none of them (with the possible exception of the very broad #3) applies in this case.

The question "How can I make my bands brighter on an agarose gel?" assumes that you've performed the agarose gel electrophoresis correctly. For instance, trivial answers like "don't use the wrong illuminator" or "don't use agar instead of agarose" or "don't forget to add the EtBr" should be precluded.

Or should they? Should the linked question be considered off-topic, by analogy to the StackExchange rule?


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There is a bit of a difference between a typo in the code on SO and the example here on Biology. There are far too many different kinds of typos you can make in a program for the question to be useful to anyone else. There is a rather limited set of mistakes you can make that result in a gel without bands.

An answer that explains possible reasons for the absence of bands is a useful resource. Even in this case where it is a rather simple error, knowing that many imaging systems can be set to different wavelengths and that this might be a problem is useful to know.

I don't think trivial mistakes should be excluded from a troubleshooting answer. To use a different example, if someone tells you that their internet is not working, checking if the network cable is plugged in or the WiFi is turned off via a button on a notebook would be the first thing I'd check. Those are trivial mistakes, but they are easy to make and excluding them is useful. We can't mention every obscure mistake one could make, but the mistakes that are trivial, but easy to make should be mentioned.

I suspect that at some point in the future we have enough questions of this kind that we will end up with a canonical troubleshooting answer for this topic. And that would certainly be a useful resource.


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