Here's why:

* Recessive traits are only expressed when an individual inherits two copies of the recessive allele for that trait.

* Dominant traits, on the other hand, are expressed even if only one copy of the dominant allele is present.

Example:

* Brown eyes are dominant over blue eyes.

* If a person inherits one allele for brown eyes (B) and one allele for blue eyes (b), they will have brown eyes because the brown eye allele is dominant.

* They still carry the blue eye allele, which is considered recessive.

* However, the blue eye trait is only expressed if the person inherits two copies of the blue eye allele (bb).

So, in a nutshell, the trait "covered over" or "dominated" is the recessive trait.