In some cases, one gene of a pair always exerts its effects, overriding the potential influence of the other gene. this is the principle.

In some cases, one gene of a pair always exerts its effects, overriding the potential influence of the other gene. This is the dominant recessive gene principle.

Some gene will have a stronger tendency to be expressed than the other. This gene will be called dominant, while the repressed gene would be called recessive. This could be happen because the dominant gene produce a functional protein while the recessive not. By examining the genetic inheritance, you could determine which gene is dominant or recessive.