[epistasis]

This is an entirely different issue than code; code mostly does the same thing when you run it twice. There's no such guarantee in biology. A cancer cell line growing in one lab may behave differently than descendants of those cells in a different lab. This may be due to slight differences in the timings between feeding the cells and the experiments, stochastic responses built into the biology, slight variations between batches of input materials for the cells, mutations in the genomes as the cell line grows, or even mistaking one cell line for another.

Reproducibility of software is a truly trivial problem in comparison.

[Someone]

Also, sometimes, doing the experiment is extremely hard. I know a guy who only slightly jokingly claims he got his Ph.D. on one brain cell. He spent a couple of years building a setup to measure electrical activity of neurons, and 'had' one cell for half an hour or so (you stick an electrode in a cell, hope it doesn't die in the process, and then hope your subject animal remains perfectly subdued, and that there will not be external vibrations that make your electrode move, thus losing contact with the cell or killing it)

Reproducible? Many people could do it, if they made the effort, but how long it would take is anybody's guess.

Experiments like that require a lot of fingerspitzengefühl from those performing them. Worse, that doesn't readily translate between labs. For example, an experimental setup in a small lab might force an experimenter in a body posture that makes his hand vibrate less when doing the experiment. If he isn't aware of that advantage, he will not be able to repeat his experiment in a better lab (I also know guys who jokingly stated they got best results with a slight hangover; there might have been some truth in that)

[campnic]

Oh, I agree. Biological experiment reproducibility is an incredibly hard problem. You are probably right that it is 'trivial' by comparison in the same way that landing on mars is trivial to landing on Alpha Centauri.

[shabble]

Not to mention the ever-present zombie threat[1][2]

[1] https://www.ncbi.nlm.nih.gov/pubmed/10516762?dopt=Citation

[2] https://en.wikipedia.org/wiki/List_of_contaminated_cell_line...