Q: Watson and Crick walked into a pet store. There were three dogs in three cages: one on the right, one on the left and one in the centre. They bought the one in the centre. Why?
A: It was the central dog, mah.
Q: Why do med students produce so much NO during exam time?
A: Because of the shear stress.
Q: Which of the salivary glands is the most boring, and why?
A: The parotid glands. Because they are totally serous.
Q: Why are zymogens so typically male enzymes?
A: Because they are turned on by cleavage.
Q: Why do you need the help of DNA Polymerase I to understand my jokes?
A: It's capable of nick translation.