Here's why:
* Genes come in pairs: Organisms inherit one gene for a trait from each parent.
* Dominant and recessive alleles: Genes can have different versions called alleles. Some alleles are dominant, meaning they are expressed even if only one copy is present. Others are recessive, meaning they are only expressed if two copies are present.
* Recessive trait expression: If an organism has two copies of the recessive allele, it will express the recessive trait.
For example, let's say brown fur is dominant (B) and white fur is recessive (b).
* An organism with BB or Bb will have brown fur.
* An organism with bb will have white fur.
