Here's why:
* Dominant genes: These genes exert their effect even if only one copy is present. They "mask" the expression of the recessive gene.
* Recessive genes: These genes only express their trait if two copies of the gene are present. If a dominant gene is present, the recessive gene's effect is hidden.
Example:
* Eye color: Brown eyes are dominant over blue eyes. So, if someone has one gene for brown eyes and one gene for blue eyes, they will have brown eyes because the brown eye gene is dominant. The blue eye gene is recessive and not expressed.
