How do recessive alleles manifest in an individual's traits?

Recessive alleles manifest in an individual's traits by requiring two copies of that allele for the trait to be expressed. This means that an individual must inherit the recessive allele from both parents to display the associated trait. If only one copy of the recessive allele is present along with a dominant allele, the dominant allele will mask the effects of the recessive one, resulting in the dominant trait being expressed instead.

For example, consider a trait like flower color in a plant species where purple is dominant (represented by the allele P) and white is recessive (represented by the allele p). A plant with the genotypes PP or Pp will have purple flowers, whereas only a plant with the genotype pp will have white flowers. This illustrates how recessive alleles operate at a genetic level and determine physical traits only when two copies are present.

Understanding this concept is crucial in genetics because it demonstrates how traits are inherited and can skip generations if an individual carries a recessive allele without expressing it themselves.