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No, I meant rather what between-different-fields-of-biology observations you might have. It doesn't matter what you study, specifically. It's more like 'but why did those biochists study the impact of gall on probiotics for a whole fortnight of cultivation, if every physiologist knows that the probiotic pill cannot possibly be stuck in the GI tract for so long? thing.' Have you encountered this before?
I can come up with a few examples that seemed obvious that they wouldn't work in retrospect, mostly having to do with gene insertion using A. tumefaciens, but none that I honestly predicted before I learned that they didn't work. Generally, the biological research at my institution seemed to be pretty practical, if boring. On the other hand, I was an undergrad, so there may have been obvious mistakes I missed -- that's part of what I'd be interested in learning.