Blood type inheritance is determined by genes inherited from parents. There are four main blood types: A, B, AB, and O. Each person has two alleles, one from each parent, which can be either A, B, or O. The combination of these alleles determines an individual's blood type. For example, if one parent has blood type A (genotype AA or AO) and the other has blood type B (genotype BB or BO), their children could inherit blood types A, B, AB, or O. The Rh factor, which indicates whether blood is positive or negative, is also inherited separately.