Blood Groups and Transfusion Medicine Practice Questions Flashcards
A family with mother and two children has been blood-typed with the following results: Mother is A-Rh+, the daughter is B-Rh-, and the son is A-Rh+. Is this possible?
A) Yes, but only with two different fathers
B) No, there has to be an error in the blood type for the daughter
C) Yes, the father must have been BO and Rh-/Rh- homozygote
D) Yes, the father must have been BO or AB with one allele Rh-
E) Yes, the father must have been BO and Rh+
D
Remember that A and B are dominant over O, and that Rh+ is dominant over Rh-. The daughter must have the genotype BO-Rh-Rh-. The O must have come from the mother, while the B comes from the father, however, he must have given either O or A to the son. The daughter has received one Rh- from each parent and we therefore know that the mother must be Rh+Rh-, but we have no information of what the second Rh allele is in the father.
Which of the following best describes the underlying reason for the difference between a person with blood type A and one with blood type B?
A) Amino acid substitutions in the galactosyl transferase
B) Inactivation of the Fucose transferase
C) Frameshift mutation in the galactosyl transferase
D) Differential ability to produce sugars D-galactose or N-acetylgalactosamine
E) Expression of Fucose transferase type 1 versus type 2 leading to use of different substrate structures
A
The difference between antigens in blood type A versus blood type B is the presence of either D-galactose or N-acetylgalactosamine. The underlying difference is that these two are used as substrates by two different variants of the galactosyl transferase, and those variants differ in the amino acid content (4 aa difference). A) is therefore the correct answer. Other answer choices: B) is the cause of O-Bombay, C) is the cause of regular blood type O, D) – I am not sure which effects this would have on the body but not difference between blood type A or B, E) is closest to the underlying cause behind being an ABO secretor or not.
A 34-year-old man receives a blood transfusion for the first time in his life. His blood type is A-Rh- and in the Lewis system he has Le(a-b+). The blood chosen for him is A-Rh- but it has Le(a+b+). What is the most likely outcome of this transfusion?
A) He has no preformed anti-Le(a+) antibodies but might develop delayed hemolytic reaction
B) He has preformed anti-Le(a+) antibodies and therefore will show an acute hemolytic reaction
C) There is a mismatch in the Rhesus blood group and he therefore will have acute hemolytic reaction
D) There is no mismatch in the ABO and Rhesus systems so no reaction is possible
A
In a properly prepared blood transfusion, blood from the recipient is mixed with the donor blood to check that there are no preformed antibodies that can produce an acute reaction. Therefore, answer B is less likely than answer A, but B could in principle be correct if someone screwed up. Answer A shows correctly that it is possible to make a delayed reaction against any of the other (not ABO) blood types. C is wrong because the blood type is matched between donor and recipient for the Rhesus system and also because a mismatch in Rhesus is likely to result in delayed hemolytic reaction unless there has been prior exposure. D is wrong because reactions can happen due to the other blood type systems.
In the archives of the genetic counseling clinic, you find an older case where one woman pointed to three possible fathers of her newborn child. Blood types of the people involved are given below. Which of the statements are most likely to be true?
Mother: A-Rh+
Child: B-Rh-
Potential 1: B-Rh+
Potential 2: O-Rh-
Potential 3: AB-Rh-
A) None of the potentials would be correct
B) Could be any of the three
C) Potential 2 is the father
D) Potential 3 is the father
E) Potential 1, 3 are both possible
E
The child must have received a B allele and an Rh- allele from the father. Potential 2 does not have a B-allele and is out, while potentials 1 and 3 both could give a B allele. It is obvious that potential 3 could have given the Rh- allele, but potential 1 could easily be a heterozygote (Rh+Rh-) and as such cannot be excluded at this point. (In the general US population there is a slightly higher frequency of Rh+Rh- heterozygotes compared with Rh+Rh+ homozygotes).
A Rhesus negative first-time mother gives birth to a Rh+ offspring and she is promptly injected with anti-D antibodies. Why is this done?
A) To improve her milk production
B) To improve the passive immunity in her milk
C) To counter the Rhesus antibodies that might have crossed the placenta
D) To induce lysis of any fetal RBC that might have crossed the placenta
E) To avoid this child getting hemolytic disease of the newborn
D
Anti-d antibodies and anti-Rhesus antibodies – two names for the same thing. Therefore, answer C makes no sense. The same can be said about answers A and B. The current child would not be affected even if nothing was done, so that leaves answer D as the correct answer. The purpose of the antibody treatment is to avoid the mother starting to produce anti-Rhesus antibodies. If she started to produce those, her next offspring could be at risk. The way to avoid her producing those antibodies is to induce breakdown of those fetal cells that carry Rhesus antigen on their surface that might have crossed the placenta, and induce that breakdown before the immune system discover that something foreign is there.
A woman with type M blood and a man with type N blood have two children with type MN blood. What is demonstrated here?
A. homozygosity
B. codominance
C. pleiotropy
D. epistasis
B
Even without any prior knowledge of the MN blood type system, it should be possible to figure out that B is the best answer.
