From both parents
Parents each pass half their ladder like dna
to baby, the dna divides lengthwise with half a rung/parent.
If half a rung is a dominent gene, the parent has the problem & passes it. If it takes 1 half from each parent to pass, it is a recessive problem & parents are not affected.Cf is carried in an estimated 1/20 unaffected people. A carrier couple can produce carrier/affected or normal kids.