CHS PRACTICE EXAM CERTIFIED
HISTOCOMPATIBILITY SPECIALIST 200
QUESTIONS ACTUAL PAPER 2026
COMPLETE QUESTIONS AND ANSWERS
GRADED A+
⩥ A sample with a new HLA-B allele arrives in the laboratory. It has a
point mutation in a region of exon 3 that had previously been considered
monomorphic. What technique would be most likely to detect the new
allele?
a) PCR-SSP
b) PCR-SSOP
c) SBT
d) RFLP
e) Anomalous linkage disequilibrium with HLA-Cw. Answer: c) SBT
⩥ A bone marrow patient is
A1,A11,B62,B64,DRB1*0103,DRB1*150101. Which of the following
potential donors is the best match?
a) A1,Blank,B62,B64,DRB1*0103,DRB1*1503
b) A1,A11,B7,B8,DR5,DR6
,c) A1,A11,B*1401,B*15,DRB1*0103,DRB1*1501
d) A1,A9,B14,B15,DR1,DR15
e) A1,A11,B14,B15,DRB1*0102,DRB1*1502. Answer: c)
A1,A11,B*1401,B*15,DRB1*0103,DRB1*1501
⩥ Which of the listed probes will have the highest Tm?
a) AACTAGTTA
b) CTATGGATCGTTGGCTACTCT
c) GTAGATTATATTACTCTAGCA
d) AACTAGTTC
e) ATATATATAT. Answer: b) CTATGGATCGTTGGCTACTCT
⩥ Primers and probes bind to their DNA targets through a process
known as
a) High stringency
b) Hydrogen bonding
c) Covalent bonding
d) Primer dimerism
e) Low Stringency. Answer: b) Hydrogen bonding
,⩥ Which is true of the 3' and/or 5' ends of an oligonucleotide primer?
a) The 3' and 5' ends always have purines
b) The 3' and 5' ends always have pyrimidines
c) The 3' and 5' ends may both serve as an template for Taq elongation
d) The 3' end may accept GTP in the presence of a DNA polymerase
e) The 5' end is the critical portion for determining the specificity of a
primer. Answer: d) The 3' end may accept GTP in the presence of a DNA
polymerase
⩥ Which of the following is true regarding the DNA polymerase used in
PCR?
a) The enzyme should only accept nucleotide diphosphates
b) The enzyme should have low fidelity
c) The enzyme should denature at 37oC
d) Isomerase enzymes should be able to switch strands
e) The enzyme should not be heat labile. Answer: e) The enzyme should
not be heat labile
⩥ Which of the following activities should be performed post-PCR?
a) Amplification, probing, high stringency wash
, b) DNA extraction, low stringency wash, probing
c) Gel electrophoresis, probing, primer aliquotting
d) Amplification, probing, primer aliquotting
e) DNA extraction, high stringency wash, primer synthesis. Answer: a)
Amplification, probing, high stringency wash
⩥ Which statement best explains the "N" suffix sometimes seen with
DNA HLA allele nomenclature?
a) Some alleles are not typeable by molecular methods
b) Some alleles are not typeable by serological methods
c) Serology and DNA sometimes arrive at different typings
d) Mutations may prevent an HLA allele from being expressed
e) Suffixes in molecular nomenclature distinguish class II from Class III
alleles. Answer: d) Mutations may prevent an HLA allele from being
expressed
⩥ SSP primers usually target what?
a) IgG Fc regions
b) Hypervariable regions
c) Unique intronic sequences
d) Conserved regions
HISTOCOMPATIBILITY SPECIALIST 200
QUESTIONS ACTUAL PAPER 2026
COMPLETE QUESTIONS AND ANSWERS
GRADED A+
⩥ A sample with a new HLA-B allele arrives in the laboratory. It has a
point mutation in a region of exon 3 that had previously been considered
monomorphic. What technique would be most likely to detect the new
allele?
a) PCR-SSP
b) PCR-SSOP
c) SBT
d) RFLP
e) Anomalous linkage disequilibrium with HLA-Cw. Answer: c) SBT
⩥ A bone marrow patient is
A1,A11,B62,B64,DRB1*0103,DRB1*150101. Which of the following
potential donors is the best match?
a) A1,Blank,B62,B64,DRB1*0103,DRB1*1503
b) A1,A11,B7,B8,DR5,DR6
,c) A1,A11,B*1401,B*15,DRB1*0103,DRB1*1501
d) A1,A9,B14,B15,DR1,DR15
e) A1,A11,B14,B15,DRB1*0102,DRB1*1502. Answer: c)
A1,A11,B*1401,B*15,DRB1*0103,DRB1*1501
⩥ Which of the listed probes will have the highest Tm?
a) AACTAGTTA
b) CTATGGATCGTTGGCTACTCT
c) GTAGATTATATTACTCTAGCA
d) AACTAGTTC
e) ATATATATAT. Answer: b) CTATGGATCGTTGGCTACTCT
⩥ Primers and probes bind to their DNA targets through a process
known as
a) High stringency
b) Hydrogen bonding
c) Covalent bonding
d) Primer dimerism
e) Low Stringency. Answer: b) Hydrogen bonding
,⩥ Which is true of the 3' and/or 5' ends of an oligonucleotide primer?
a) The 3' and 5' ends always have purines
b) The 3' and 5' ends always have pyrimidines
c) The 3' and 5' ends may both serve as an template for Taq elongation
d) The 3' end may accept GTP in the presence of a DNA polymerase
e) The 5' end is the critical portion for determining the specificity of a
primer. Answer: d) The 3' end may accept GTP in the presence of a DNA
polymerase
⩥ Which of the following is true regarding the DNA polymerase used in
PCR?
a) The enzyme should only accept nucleotide diphosphates
b) The enzyme should have low fidelity
c) The enzyme should denature at 37oC
d) Isomerase enzymes should be able to switch strands
e) The enzyme should not be heat labile. Answer: e) The enzyme should
not be heat labile
⩥ Which of the following activities should be performed post-PCR?
a) Amplification, probing, high stringency wash
, b) DNA extraction, low stringency wash, probing
c) Gel electrophoresis, probing, primer aliquotting
d) Amplification, probing, primer aliquotting
e) DNA extraction, high stringency wash, primer synthesis. Answer: a)
Amplification, probing, high stringency wash
⩥ Which statement best explains the "N" suffix sometimes seen with
DNA HLA allele nomenclature?
a) Some alleles are not typeable by molecular methods
b) Some alleles are not typeable by serological methods
c) Serology and DNA sometimes arrive at different typings
d) Mutations may prevent an HLA allele from being expressed
e) Suffixes in molecular nomenclature distinguish class II from Class III
alleles. Answer: d) Mutations may prevent an HLA allele from being
expressed
⩥ SSP primers usually target what?
a) IgG Fc regions
b) Hypervariable regions
c) Unique intronic sequences
d) Conserved regions
