When both a dominant and recessive gene are present in a pair, the dominant gene is expressed.

Here's why:

* Dominant genes are like "stronger" versions of the trait. They exert their influence even when paired with a recessive gene.

* Recessive genes are like "weaker" versions of the trait. They are only expressed if there are two copies of the recessive gene present (one from each parent).

For example, let's say brown eyes are dominant (B) and blue eyes are recessive (b):

* BB: Brown eyes (both genes are dominant)

* Bb: Brown eyes (the dominant gene "overpowers" the recessive gene)

* bb: Blue eyes (both genes are recessive)

So, even if someone carries the gene for blue eyes (b), they will still have brown eyes if they also carry the gene for brown eyes (B).