How can a recessive gene show back up after several generations

Only individuals with an aa genotype will express a recessive trait; therefore, offspring must receive one recessive allele from each parent to exhibit a recessive trait ... If one parent is heterozygous (Ss) and the other is homozygous recessive (ss), then half of their offspring will have a smooth chin.

Recessive traits like red hair can skip generations because they can hide out in a carrier behind a dominant trait