ASCP CG Certification Practice Questions Actual Exam
2026/2027 with Detailed Rationales | Complete Exam-Style
Questions | Graded A+ Pass Guaranteed
Total Questions: 50 | Time: 90 min | Pass: 80%
TABLE OF CONTENTS
Section 1 | Cytogenetics Fundamentals & Laboratory Safety | Q1 – Q10
Section 2 | Chromosome Structure, Banding, & Karyotype Analysis | Q11 – Q20
Section 3 | Constitutional Cytogenetics & Syndromic Disorders | Q21 – Q30
Section 4 | Acquired Cytogenetics & Oncology Applications | Q31 – Q40
Section 5 | Molecular Cytogenetics (FISH, Microarrays) & Quality Assurance | Q41 – Q50
Instructions: Choose the single best answer. Pass: 80% in 90 minutes.
══════════════════════════════════════
SECTION 1: CYTOGENETICS FUNDAMENTALS & LABORATORY SAFETY Q1 – Q10
══════════════════════════════════════
Question 1 of 50
A 28-year-old cytogenetics technologist has been working in the harvest area for three
hours and notices throat irritation and watery eyes. She realizes the fume hood was not
turned on while she was changing fixative solutions. The most likely cause of her
symptoms is exposure to:
A. Giemsa stain, because it causes methemoglobinemia when inhaled.
B. Glacial acetic acid and methanol vapors, because the 3:1 fixative mixture is highly
volatile and irritating to mucous membranes. ✓ CORRECT
C. Colcemid, because it is a potent neurotoxin absorbed through skin contact.
D. Trypsin, because aerosolized protease causes respiratory sensitization.
Correct Answer: B
Rationale: The 3:1 methanol:glacial acetic acid fixative is extremely volatile and
produces irritating vapors that cause mucous membrane irritation when used outside a
,functioning fume hood. Colcemid is toxic but primarily through ingestion or skin
absorption, and it does not typically cause acute throat irritation. Proper ventilation is
essential during harvest and fixation procedures to prevent occupational exposure.
Question 2 of 50
A prenatal specimen of 25 mL amniotic fluid arrives at the cytogenetics laboratory at
3:00 PM on Friday from a clinic two hours away. The requisition indicates the fluid was
collected at 1:00 PM. The most appropriate immediate action for the technologist is to:
A. Refrigerate the specimen at 4°C until processing on Monday morning.
B. Freeze the specimen at -20°C to preserve cell viability over the weekend.
C. Add colcemid to the fluid to arrest cells in metaphase before the weekend.
D. Process the specimen immediately or store it at room temperature for processing
within 24 hours, because amniotic fluid cells lose viability rapidly if refrigerated or
frozen. ✓ CORRECT
Correct Answer: D
Rationale: Amniotic fluid specimens should be processed within 24 hours and
maintained at room temperature because refrigeration or freezing damages fetal cell
viability and compromises culture success. Adding colcemid to uncultured fluid is
inappropriate and would kill the cells rather than prepare them for analysis. Prenatal
laboratories typically process amniotic fluid on the day of receipt to maximize the
chance of establishing viable cultures.
Question 3 of 50
A technologist sets up a peripheral blood culture for a 6-year-old patient with
developmental delay. She adds the patient's blood to culture medium and incubates it,
but after 72 hours, the harvest yields no metaphase cells. The most likely explanation
for the culture failure is:
,A. Failure to add phytohemagglutinin (PHA), because T-lymphocytes in peripheral blood
require PHA mitogenic stimulation to divide in vitro. ✓ CORRECT
B. Use of a 37°C incubator instead of 35°C, because blood cultures require cooler
temperatures for optimal growth.
C. Addition of too much colcemid, because excess mitotic inhibitor prevents cells from
entering metaphase.
D. Use of RPMI medium instead of Chang medium, because blood cultures require
specialized amniotic fluid medium.
Correct Answer: A
Rationale: Peripheral blood lymphocytes are non-dividing cells in vivo and require PHA
stimulation to enter the cell cycle and reach metaphase in culture; without it, no
divisions occur. While colcemid excess can affect chromosome morphology, it does not
prevent cells from entering metaphase entirely. Blood cultures are routinely established
in RPMI-based medium with PHA supplementation.
Question 4 of 50
A technologist is harvesting bone marrow cells from a patient with suspected acute
leukemia. She adds colcemid to the culture for 20 minutes before adding hypotonic
solution. The purpose of the colcemid treatment is to:
A. Lyse red blood cells and isolate white blood cells for culture.
B. Fix the chromosomes to preserve their structure during slide preparation.
C. Arrest dividing cells in metaphase by inhibiting microtubule polymerization, thereby
accumulating analyzable chromosomes. ✓ CORRECT
D. Swell the cells to spread the chromosomes apart on the slide.
Correct Answer: C
Rationale: Colcemid (demecolcine) is a mitotic inhibitor that prevents spindle formation
by disrupting microtubule polymerization, causing cells to arrest at metaphase where
chromosomes are most condensed and analyzable. Hypotonic solution, not colcemid,
causes cell swelling to spread chromosomes. Fixation occurs after hypotonic treatment
using methanol:glacial acetic acid.
, Question 5 of 50
During a routine bone marrow harvest, a new technologist accidentally uses isotonic
saline instead of the standard 0.075 M potassium chloride solution prior to fixation. The
most likely consequence on the final chromosome preparations is:
A. The chromosomes will be over-condensed and appear too dark after staining.
B. The cells will not swell adequately, resulting in chromosomes that overlap and are
difficult to separate for analysis. ✓ CORRECT
C. The chromosomes will be fragmented due to osmotic shock.
D. The Giemsa stain will not adhere to the chromosomes properly.
Correct Answer: B
Rationale: Hypotonic KCl solution causes cells to swell, which spreads the
chromosomes apart and reduces overlap on the metaphase spread; isotonic saline
maintains normal cell volume and produces overlapping chromosomes. Chromosome
condensation is controlled by colcemid timing and culture conditions, not by the
hypotonic solution. Proper spreading is essential for accurate karyotype analysis.
Question 6 of 50
A technologist is checking cell cultures on day 3 after setup. She places the culture
flask on an inverted microscope and adjusts the optics to examine cell growth and
morphology without staining. The type of microscopy she is using is:
A. Bright-field microscopy, because unstained cells are viewed with transmitted white
light.
B. Fluorescence microscopy, because UV light is used to excite natural cellular
fluorophores.
C. Electron microscopy, because subcellular detail is required for culture assessment.
D. Phase-contrast microscopy, because it enhances contrast in living, unstained cells by
exploiting differences in refractive index. ✓ CORRECT
Correct Answer: D
2026/2027 with Detailed Rationales | Complete Exam-Style
Questions | Graded A+ Pass Guaranteed
Total Questions: 50 | Time: 90 min | Pass: 80%
TABLE OF CONTENTS
Section 1 | Cytogenetics Fundamentals & Laboratory Safety | Q1 – Q10
Section 2 | Chromosome Structure, Banding, & Karyotype Analysis | Q11 – Q20
Section 3 | Constitutional Cytogenetics & Syndromic Disorders | Q21 – Q30
Section 4 | Acquired Cytogenetics & Oncology Applications | Q31 – Q40
Section 5 | Molecular Cytogenetics (FISH, Microarrays) & Quality Assurance | Q41 – Q50
Instructions: Choose the single best answer. Pass: 80% in 90 minutes.
══════════════════════════════════════
SECTION 1: CYTOGENETICS FUNDAMENTALS & LABORATORY SAFETY Q1 – Q10
══════════════════════════════════════
Question 1 of 50
A 28-year-old cytogenetics technologist has been working in the harvest area for three
hours and notices throat irritation and watery eyes. She realizes the fume hood was not
turned on while she was changing fixative solutions. The most likely cause of her
symptoms is exposure to:
A. Giemsa stain, because it causes methemoglobinemia when inhaled.
B. Glacial acetic acid and methanol vapors, because the 3:1 fixative mixture is highly
volatile and irritating to mucous membranes. ✓ CORRECT
C. Colcemid, because it is a potent neurotoxin absorbed through skin contact.
D. Trypsin, because aerosolized protease causes respiratory sensitization.
Correct Answer: B
Rationale: The 3:1 methanol:glacial acetic acid fixative is extremely volatile and
produces irritating vapors that cause mucous membrane irritation when used outside a
,functioning fume hood. Colcemid is toxic but primarily through ingestion or skin
absorption, and it does not typically cause acute throat irritation. Proper ventilation is
essential during harvest and fixation procedures to prevent occupational exposure.
Question 2 of 50
A prenatal specimen of 25 mL amniotic fluid arrives at the cytogenetics laboratory at
3:00 PM on Friday from a clinic two hours away. The requisition indicates the fluid was
collected at 1:00 PM. The most appropriate immediate action for the technologist is to:
A. Refrigerate the specimen at 4°C until processing on Monday morning.
B. Freeze the specimen at -20°C to preserve cell viability over the weekend.
C. Add colcemid to the fluid to arrest cells in metaphase before the weekend.
D. Process the specimen immediately or store it at room temperature for processing
within 24 hours, because amniotic fluid cells lose viability rapidly if refrigerated or
frozen. ✓ CORRECT
Correct Answer: D
Rationale: Amniotic fluid specimens should be processed within 24 hours and
maintained at room temperature because refrigeration or freezing damages fetal cell
viability and compromises culture success. Adding colcemid to uncultured fluid is
inappropriate and would kill the cells rather than prepare them for analysis. Prenatal
laboratories typically process amniotic fluid on the day of receipt to maximize the
chance of establishing viable cultures.
Question 3 of 50
A technologist sets up a peripheral blood culture for a 6-year-old patient with
developmental delay. She adds the patient's blood to culture medium and incubates it,
but after 72 hours, the harvest yields no metaphase cells. The most likely explanation
for the culture failure is:
,A. Failure to add phytohemagglutinin (PHA), because T-lymphocytes in peripheral blood
require PHA mitogenic stimulation to divide in vitro. ✓ CORRECT
B. Use of a 37°C incubator instead of 35°C, because blood cultures require cooler
temperatures for optimal growth.
C. Addition of too much colcemid, because excess mitotic inhibitor prevents cells from
entering metaphase.
D. Use of RPMI medium instead of Chang medium, because blood cultures require
specialized amniotic fluid medium.
Correct Answer: A
Rationale: Peripheral blood lymphocytes are non-dividing cells in vivo and require PHA
stimulation to enter the cell cycle and reach metaphase in culture; without it, no
divisions occur. While colcemid excess can affect chromosome morphology, it does not
prevent cells from entering metaphase entirely. Blood cultures are routinely established
in RPMI-based medium with PHA supplementation.
Question 4 of 50
A technologist is harvesting bone marrow cells from a patient with suspected acute
leukemia. She adds colcemid to the culture for 20 minutes before adding hypotonic
solution. The purpose of the colcemid treatment is to:
A. Lyse red blood cells and isolate white blood cells for culture.
B. Fix the chromosomes to preserve their structure during slide preparation.
C. Arrest dividing cells in metaphase by inhibiting microtubule polymerization, thereby
accumulating analyzable chromosomes. ✓ CORRECT
D. Swell the cells to spread the chromosomes apart on the slide.
Correct Answer: C
Rationale: Colcemid (demecolcine) is a mitotic inhibitor that prevents spindle formation
by disrupting microtubule polymerization, causing cells to arrest at metaphase where
chromosomes are most condensed and analyzable. Hypotonic solution, not colcemid,
causes cell swelling to spread chromosomes. Fixation occurs after hypotonic treatment
using methanol:glacial acetic acid.
, Question 5 of 50
During a routine bone marrow harvest, a new technologist accidentally uses isotonic
saline instead of the standard 0.075 M potassium chloride solution prior to fixation. The
most likely consequence on the final chromosome preparations is:
A. The chromosomes will be over-condensed and appear too dark after staining.
B. The cells will not swell adequately, resulting in chromosomes that overlap and are
difficult to separate for analysis. ✓ CORRECT
C. The chromosomes will be fragmented due to osmotic shock.
D. The Giemsa stain will not adhere to the chromosomes properly.
Correct Answer: B
Rationale: Hypotonic KCl solution causes cells to swell, which spreads the
chromosomes apart and reduces overlap on the metaphase spread; isotonic saline
maintains normal cell volume and produces overlapping chromosomes. Chromosome
condensation is controlled by colcemid timing and culture conditions, not by the
hypotonic solution. Proper spreading is essential for accurate karyotype analysis.
Question 6 of 50
A technologist is checking cell cultures on day 3 after setup. She places the culture
flask on an inverted microscope and adjusts the optics to examine cell growth and
morphology without staining. The type of microscopy she is using is:
A. Bright-field microscopy, because unstained cells are viewed with transmitted white
light.
B. Fluorescence microscopy, because UV light is used to excite natural cellular
fluorophores.
C. Electron microscopy, because subcellular detail is required for culture assessment.
D. Phase-contrast microscopy, because it enhances contrast in living, unstained cells by
exploiting differences in refractive index. ✓ CORRECT
Correct Answer: D
