Genes are called dominant because they express their trait even when only one copy of that gene is present. This means that even if an individual inherits one dominant allele and one recessive allele, the trait associated with the dominant allele will be expressed.

Here's a simple breakdown:

* Alleles: Different versions of the same gene.

* Dominant allele: An allele that masks the effect of the recessive allele.

* Recessive allele: An allele whose effect is masked by the dominant allele.

For example, let's consider brown eyes (dominant) and blue eyes (recessive).

* BB: Individual has two dominant alleles (brown eyes).

* Bb: Individual has one dominant and one recessive allele (brown eyes).

* bb: Individual has two recessive alleles (blue eyes).

In the Bb case, even though the individual carries one blue-eyed allele, their eyes will still be brown because the brown-eyed allele is dominant. This is why some genes are called dominant. They exert their influence even when paired with a different allele.

Here's a key takeaway: Dominance doesn't mean the dominant allele is "better" or "stronger" than the recessive allele. It just means its effect is more noticeable.