I Assumed...

To do a ligation experiment, you mix the enzyme and the DNA in an Eppendorf tube, put it in a PCR machine and leave it at 16 degrees overnight. A PCR machine is basically a metal block whose temperature you can control, from 0 degree to over 100 degrees. You can also control how long it holds a certain temperature, from several seconds to several days. You can save your settings to a program and assign a number to it. For example, the number for the ligation is 6. Next time you want to use the same program you can just browse to the number and hit the "RUN!" button.

Today, Feng felt ready for a ligation. He put his tubes into the PCR machine and turned it on. Without looking at the LCD display, which showed the program number and its settings, he hit the "RUN!" button. Instead of leisurely holding at 16 degrees, the machine made some labored noises, turned off its green light then turned on a red one, and heated its metal block to 95 degrees within a few seconds. Feng noticed the machine's fiery manner and checked the LCD. Of course, the machine was not on program 6, but on some other program whose first step was 95 degrees for 5 minutes. He panicked a little and shut it down 3 seconds later.

When he turned around to make sure no one saw it, Feng met the boss's smiling face. Apparently, he saw the whole thing.

"Errr..."Feng tried to explain,"I just assumed it was on the right program!"

"You assumed,"the boss grabbed a pen and wrote the word ASSUME down on a piece of paper, "look, when you ASSUME something, you make an ASS out of U and ME!"

That's a good one.