If a patient is npo at midnight the night before their scheduled surgery, what does this mean?

It means that they cannot eat or drink the night before the surgery. By doing this, it makes it easier for the doctors to perform the operation in an empty stomach. Another reason why it is required is because you will feel extremely nausea after the surgery if you eat because your body is still digesting the food even when you just had breathed in anesthesia 

The punnett square is the device used to predict genetics.