Can parents who are B positive and AB positive have a B negative child?

Yes D = Rh+, d = Rh- If both parents are heterozygous (D d), then the baby can get d from each; therefore, resulting in Rh- Also can get D from 1 parent & d from other parent resulting in Rh+ Or can get D from each parent, resulting in Rh+ As for B & AB, The parent which is type B has genotype of BO or BB both of which would result in B type. AB parent has only 1 option for genotype, AB The baby gets 1 gene from each parent, so possibilities for baby are: AB, B (genotype BO or BB; B is dominant), A (genotype AO; A is dominant) This baby could be type A+ A- B+ B- AB+ or AB-