"In It Goes!"
5 November 2025
It was a beautiful sunny afternoon. I was a demonstrator in room full of students working through a straightforward cloning practical: insert lacZ into an expression vector, transform some DH5α cells, and screen for successful clones using the classic blue/white selection on X-Gal/IPTG plates.
On this sunny day, the students had already purified cut vector and insert, and they were suppose to mix their ligation reaction together and pop them in a 15°C water bath overnight.
The afternoon had been progressing as smoothly as can be expected for a group practical. Groups of students completed their pipetting, dutifully trooped over to the water bath with their precious reaction tubes, and placed them carefully in the water bath where T4 DNA ligase would work its enzymatic magic overnight. A small crowd had gathered around the bath, that peculiar mixture of achievement and impatience that comes with being done while others are still pipetting.
Finally we were waiting for just a single group of two students to complete their reaction. They finished! They approached! The moment we had all been waiting for.
The supervising academic asked the obvious question: "Have you labelled your tube so that you know which is yours?"
The student hesitated, clearly puzzled by this seemingly bureaucratic requirement, but obediently pulled out a permanent marker and labeled the lid. Then I did not understand why he was so puzzled. But it would become rather clear. He looked up expectantly, marker still in hand, and asked with genuine curiosity: "And what do I do now with the reaction?"
The academic's smile widened with benign encouragement. He gestured toward the water bath and said: "Well, in it goes!"
With the confident fluidity of someone who absolutely knows what they're doing, the student flicked open the tube lid with his thumb and, before anyone could so much as inhale to shout "WAIT!", poured the entire contents of his ligation reaction directly into the water bath.
Time stopped. Around the water bath, everyone stood frozen. Somewhere in the building, a centrifuge hummed. Outside, birds sang. The water bath itself sat there innocently, now containing approximately 10 liters of water and 20 microliters of very dilute, very diffuse ligation reaction.
The academic's face cycled through several expressions in rapid succession: confusion, comprehension and finally settled on a sort of dissociative amused disbelief. His eyes were wide, his jaw had dropped. Of course the student was confused why he had to label the tube, as he thought the tube was not needed.
Finally, the academic found his voice: "But, but ... how will you get your ligation reaction OUT of the water bath tomorrow?"
It was a reasonable question. The kind of question that, when asked, usually results in the horrible dawning realization of a mistake, followed by profuse apologies and perhaps some creative problem-solving about whether there are any spare aliquots of vector and insert available.
But this student didn't miss a beat. Without even the slightest hesitation, his face brightened with the cheerful confidence of someone presenting an elegant solution to a trivial problem:
"Simple! We'll do an ethanol precipitation!"
Epilogue: For those wondering, no, you cannot practically perform an ethanol precipitation on 10 L of water bath to recover 20 μL of ligation reaction. That would require approximately 25 liters of ice-cold ethanol and a centrifuge the size of a small car, and you could never successfully recover the DNA that went in. Beside the fact that, in this sort of volume, the ligation reaction would be much more unlikely to take place. The students were given fresh aliquots of vector, insert, buffer and T4 DNA ligase.
Lessons learned: Always be painfully, explicitly specific with instructions. Never underestimate a student's ability to interpret things literally. As Douglas Adams put it in Mostly Harmless: "A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools."