18. What are the possible genotypes and phenotypes of offspring born to a mother with type A and a father with type B blood? (Hint: Recall the difference between genotype and pheno- type.) Use Punnett squares to determine percentages. 19. What does it mean when a unit of blood is "typed and cross-matched" before it is given to a patient? Why must this be done? Rh Blood Typing Questions For the following questions only consider the Rh blood type. 20. What does Rh stand for? 21. How many Rh antigens have been identified? Which Rh antigen did you test for? 22. Approximately what percentage of a population does not express Rh(D) antigen? 23. Why would prenatal care include determining the mother's but not the father's blood type? svisizoq-d