How a recessive trait can skip a generation
For many inherited traits, a person receives two copies of a gene-related variant, one from each biological parent. A recessive variant usually affects the trait only when both copies are recessive. Someone with one recessive copy and one working copy is a carrier: the working copy is typically enough to prevent the trait from appearing, even though the carrier can pass the recessive variant to a child.
Why two carriers can have an affected child
If both parents are carriers, each passes on one of their two copies at random. A child can inherit the working copy from both parents, a recessive copy from just one, or a recessive copy from both. Only that last combination produces the recessive form of the trait in the simple inheritance pattern described here.
That gives each pregnancy a one-in-four chance of producing a child with two recessive copies. It is a probability for each pregnancy—not a quota across a family. Having one affected child does not make the next child less likely to be affected, and several unaffected children do not make an affected child “due.”
What “skipping a generation” really means
The variant has not vanished in the intervening generation; it can be carried without being visible. When two carriers have a child, their inherited copies can combine to reveal the trait again. This familiar pattern applies to some conditions and traits, though inheritance is not always this simple: some traits involve multiple genes or other biological influences. Still, the key idea is straightforward: a trait can be absent in a parent’s appearance yet remain present in the variants that parent can pass on.
