1 GENETICS AND IMMUNOLOGY OF BLOOD GROUPS Flashcards
(1) What type of serological testing does the blood bank technologist perform when determining the blood group of a patient?
A. Genotyping
B. Phenotyping
C. Both genotyping and phenotyping
D. Polymerase chain reaction
B. Phenotyping
Phenotyping, or the physical expression of a genotype, is the type of testing routinely performed in the blood bank. An individual, for example, may have the AO genotype but phenotypes as group A.
(2) If anti-K reacts 3+ with a donor cell with a genotype KK and 2+ with a Kk cell, the antibody is demonstrating:
A. Dosage
B. Linkage disequilibrium
C. Homozygosity
D. Heterozygosity
A. Dosage
Dosage is defined as an antibody reacting stronger with homozygous cells (e.g., KK) than with heterozygous cells (e.g., Kk). In addition to Kell, dosage effect is seen commonly with antigens M, N, S, s, Fya, Fyb, Jka, Jkb, and the antigens of the Rh system.
(3) Carla expresses the blood group antigens Fya, Fyb, and Xga. James shows expressions of none of these antigens. What factor(s) may account for the absence of these antigens in James?
A. Gender
B. Race
C. Gender and race
D. Medication
C. Gender and race
The frequency of Duffy antigens Fya and Fyb varies with race. The Fy(a-b-) phenotype occurs in almost 70% of African Americans and is very rare in whites. Xga antigen is X-linked and, therefore, expressed more frequently in women (who may inherit the antigen from either parent) than in men.
(4) Which of the following statements is true?
A. An individual with the BO genotype is homozygous for B antigen
B. An individual with the BB genotype is homozygous for B antigen
C. An individual with the OO genotype is heterozygous for O antigen
D. An individual with the AB phenotype is homozygous for A and B antigens
B. An individual with the BB genotype is homozygous for B antigen
An individual having the BB genotype has inherited the B gene from both parents and, therefore, is homozygous for B antigen.
(5) Which genotype is heterozygous for C?
A. DCe/dce
B. DCE/DCE
C. Dce/dce
D. DCE/dCe
A. DCe/dce
The genotype DCe/dce contains one C and one c gene and is heterozygous for C and c antigens.
(6) Which genotype(s) will give rise to the Bombay phenotype?
A. HH only
B. HH and Hh
C. Hh and hh
D. hh only
D. hh only
The Bombay phenotype will be expressed only when no H substance is present. The Oh type is expressed by the genotype hh. Bombay phenotypes produce naturally occurring anti-H, and their serum agglutinates group O red blood cells (RBCs) in addition to RBCs from persons who are groups A, B, and AB.
(7) Meiosis in cell division is limited to the ova and sperm producing four gametes containing what complement of DNA?
A. 1N
B. 2N
C. 3N
D. 4N
A. 1N
Meiosis involves two nuclear divisions in succession resulting in four gametocytes, each containing half the number of chromosomes found in somatic cells or 1N.
(8) A cell that is not actively dividing is said to be in:
A. Interphase
B. Prophase
C. Anaphase
D. Telophase
A. Interphase
Interphase is the stage in between cell divisions. The cell is engaged in metabolic activity. Chromosomes are not clearly discerned; however, nucleoli may be visible.
(9) Which of the following describes the expression of most blood group antigens?
A. Dominant
B. Recessive
C. Codominant
D. Corecessive
C. Codominant
The inheritance of most blood group genes is codominant, meaning that no gene or allele is dominant over another. For example, a person who is group AB expresses both the A and B antigen on his or her RBCs.
(10) What blood type is not possible for an offspring of an AO and BO mating?
A. AB
B. A or B
C. O
D. All are possible
D. All are possible
A mating between AO and BO persons can result in an offspring with blood type A, B, AB, or O.
(11) The alleged father of a child in a disputed case of paternity is blood group AB. The mother is group O, and the child is group O. What type of exclusion is this?
A. Direct/primary/first order
B. Probability
C. Random
D. Indirect/secondary/second order
D. Indirect/secondary/second order
An indirect/secondary/second order, exclusion occurs when a genetic marker is absent in the child but should have been transmitted by the alleged father. In this case, either A or B should be present in the child.
(12) If the frequency of gene Y is 0.4 and the frequency of gene Z is 0.5, one would expect that they should occur together 0.2 (20%) of the time. In actuality, they are found together 32% of the time. This is an example of:
A. Crossing over
B. Linkage disequilibrium
C. Polymorphism
D. Chimerism
B. Linkage disequilibrium
Linkage disequilibrium is a phenomenon in which alleles situated in close proximity on a chromosome associate with one another more than would be expected from individual allelic frequencies.
(13) In the Hardy-Weinberg formula, p2 represents:
A. The heterozygous population of one allele
B. The homozygous population of one allele
C. The recessive allele
D. The dominant allele
B. The homozygous population of one allele
In the Hardy-Weinberg formula (p^2 + 2pq + q^2), p^2 and q^2 represent homozygous expressions, and 2pq represents heterozygous expression. This formula is used in population genetics to determine the frequency of different alleles.
(14) In this type of inheritance, the father carries the trait on his X chromosome. He has no sons with the trait because he passed his Y chromosome to his sons; however, all his daughters will express the trait.
A. Autosomal dominant
B. Autosomal recessive
C. X-linked dominant
D. X-linked recessive
C. X-linked dominant
In X-linked dominant inheritance, there is absence of male-to-male transmission because a male passes his Y chromosome to all of his sons and his single X chromosome to all his daughters. All daughters who inherit the affected gene will express the trait. An example of this type of inheritance is the Xga blood group.
(15) Why do immunoglobulin M (IgM) antibodies, such as those formed against ABO antigens, have the ability to directly agglutinate RBCs and cause visible agglutination?
A. IgM antibodies are larger molecules and have the ability to bind more antigen
B. IgM antibodies tend to clump together more readily to bind more antigen
C. IgM antibodies are found in greater concentrations than IgG antibodies
D. IgM antibodies are not limited by subclass specificity
A. IgM antibodies are larger molecules and have the ability to bind more antigen
An IgM molecule has the potential to bind up to 10 antigens compared with a molecule of IgG, which can bind only two.
