What is the temperature at which enzymes work best and worst?

Best-37.5 oC

There is a certain temperature at which an enzyme's catalytic activity is at its greatest (see graph). This optimal temperature is usually around human body temperature (37.5 oC) for the enzymes in human cells

Worst-temperatures above 104 degrees Fahrenheit, 40 degrees Celsius, will start to break them down

Explanation:

this is true, assuming that the allele is completely recessive and incomplete dominance is not a factor.