100+ Free CG Practice Questions

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Direct preparation of chorionic villi yields metaphases from which cell type?

Cytotrophoblast spontaneously dividing cells

Mesenchymal core fibroblasts

Maternal decidua

Amniocytes

to track

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2026 Statistics

Key Facts: CG Exam

100

CAT Items

ASCP BOC

~$270

Exam Fee

Effective Jan 2026

Scientist

Credential Level

Rebranded from Technologist

ISCN 2024

Nomenclature Standard

International System

The ASCP CG (Scientist in Cytogenetics) is a Scientist-level BOC credential. 100 CAT items, ~$270 fee (effective Jan 2026). Eligibility: bachelor's degree + NAACLS-accredited cytogenetics program OR equivalent experience routes. Master ISCN 2024 nomenclature, G-banding, FISH probes (locus-specific, centromeric, paint), and the recurring chromosomal abnormalities in hematologic malignancies and constitutional disorders.

Sample CG Practice Questions

Try these sample questions to test your CG exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which mitogen is most commonly used to stimulate T-lymphocytes for peripheral blood cytogenetic culture?

A.Phytohemagglutinin (PHA)

B.Pokeweed mitogen

C.Lipopolysaccharide

D.Concanavalin A

Explanation: Phytohemagglutinin (PHA) is the standard T-cell mitogen used in peripheral blood cultures for constitutional cytogenetics, typically harvested at 72 hours.

2What is the standard duration for harvesting a peripheral blood lymphocyte culture for constitutional karyotyping?

A.24 hours

B.48 hours

C.72 hours

D.120 hours

Explanation: Peripheral blood lymphocyte cultures are typically harvested at 72 hours after PHA stimulation, when T-cells are in optimal mitotic activity.

3Which agent is added to cytogenetic cultures to arrest cells in metaphase by inhibiting spindle formation?

A.Colcemid

B.Methotrexate

C.Thymidine

D.Trypsin

Explanation: Colcemid (demecolcine) binds tubulin and prevents spindle assembly, arresting cells in metaphase for chromosome analysis.

4What is the purpose of adding hypotonic solution (typically 0.075 M KCl) during cytogenetic harvest?

A.To swell cells and spread chromosomes

B.To fix chromosomes

C.To stain chromosomes

D.To inhibit metaphase

Explanation: Hypotonic KCl causes water to enter cells osmotically, swelling them so chromosomes spread apart when dropped onto slides.

5What is the standard fixative used in cytogenetics for chromosome preparations?

A.10% neutral buffered formalin

B.3:1 methanol:acetic acid

C.70% ethanol

D.Glutaraldehyde

Explanation: Carnoy's fixative (3:1 methanol:glacial acetic acid) is the standard for cytogenetic preparations; it preserves chromosome morphology and removes cytoplasm.

6GTG banding (G-bands by trypsin using Giemsa) produces dark bands enriched in which type of DNA?

A.GC-rich, gene-rich euchromatin

B.AT-rich, gene-poor heterochromatin

C.Centromeric satellite DNA exclusively

D.rDNA repeats only

Explanation: GTG dark bands are AT-rich, late-replicating, and gene-poor; light bands are GC-rich, early-replicating, and gene-rich.

7Which banding technique selectively stains constitutive heterochromatin around centromeres and the long arm of the Y?

A.G-banding

B.Q-banding

C.C-banding

D.R-banding

Explanation: C-banding (centromeric/constitutive heterochromatin) uses barium hydroxide and Giemsa to stain pericentromeric heterochromatin and the distal Yq.

8NOR (nucleolar organizing region) staining with silver nitrate identifies rDNA loci on the short arms of which chromosomes?

A.1, 9, 16, Y

B.13, 14, 15, 21, 22

C.X and Y

D.All metacentric chromosomes

Explanation: The five acrocentric chromosomes (13, 14, 15, 21, 22) carry rRNA gene clusters on their short arms (satellites/stalks); silver staining marks active NORs.

9To achieve high-resolution banding (>550 bands), cells are typically synchronized using which agent?

A.Methotrexate followed by thymidine release

B.Colcemid only

C.PHA increased dose

D.Trypsin pre-treatment

Explanation: Methotrexate blocks dihydrofolate reductase, arresting cells in S-phase; thymidine release synchronizes them into prometaphase, producing longer, less condensed chromosomes.

10What is the minimum number of metaphases typically counted in a standard constitutional peripheral blood karyotype?

A.5

B.10

C.20

D.50

Explanation: Per ACMG/ISCN guidelines, 20 metaphases are typically counted for a standard constitutional study; 5 are fully karyotyped.

About the CG Exam

ASCP Board of Certification Scientist-level credential for cytogenetic technologists. NOTE: ASCP rebranded the credential from 'Technologist in Cytogenetics' to 'Scientist in Cytogenetics' (CG) — the modern title. Validates expertise in chromosome analysis (G-banding, FISH, microarray), karyotype nomenclature (ISCN 2024), constitutional cytogenetics (Down/Edwards/Patau, Turner, Klinefelter, microdeletion syndromes), cancer cytogenetics (Philadelphia chromosome, APL t(15;17), MYC translocations, IGH translocations), and laboratory operations.

Questions

100 scored questions

Time Limit

Per ASCP scheduling

Passing Score

Scaled

Exam Fee

~$270 (effective Jan 2026) (ASCP BOC)

CG Exam Content Outline

25%

Cytogenetic Methods

Cell culture, harvest, banding (G/Q/R/C/NOR), FISH probes, microarray (CMA)

25%

Constitutional Cytogenetics

Pediatric and prenatal: trisomy 21/18/13, Turner, Klinefelter, microdeletion syndromes

25%

Cancer Cytogenetics

Hematologic (Philadelphia, APL, AML, lymphoma) and solid tumor recurring abnormalities

15%

Molecular Cytogenetics

Microarray (CMA — SNP, aCGH), NGS for cytogenetics, optical genome mapping

10%

Lab Operations, QC, Safety, Ethics

ISCN nomenclature, CAP/CLIA accreditation, BSL-2, mosaicism rule-out

How to Pass the CG Exam

What You Need to Know

Passing score: Scaled
Exam length: 100 questions
Time limit: Per ASCP scheduling
Exam fee: ~$270 (effective Jan 2026)

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

CG Study Tips from Top Performers

1Master ISCN 2024 karyotype nomenclature: 46,XX/XY normal; trisomy = 47 with +N; structural rearrangements t() inv() del() dup() ins() isochr

2Memorize disease-defining translocations: t(9;22) CML, t(15;17) APL, t(8;21) AML M2, inv(16) AML, t(11;14) mantle cell, t(8;14) Burkitt, t(14;18) FL

3Know FISH probe types: locus-specific (LSI), centromeric (CEP), whole chromosome paint (WCP), telomeric, subtelomeric

4Understand G-banding (most common — trypsin-Giemsa), Q-banding, R-banding, C-banding (centromeric heterochromatin), NOR (silver staining)

5Apply Hook's tables for mosaicism rule-out: minimum cell counts (typically 20 metaphases for postnatal; 50 for mosaicism rule-out)

Frequently Asked Questions

What's the difference between Cytogenetics Technologist and Scientist?

ASCP rebranded the cytogenetics credential from 'Technologist' (CG, also known as CT or T(CG)) to 'Scientist in Cytogenetics' (still abbreviated CG) — same exam, modern terminology. Some third-party references still use 'Technologist' or 'CT' but ASCP's current catalog uses 'Scientist in Cytogenetics'.

What is ISCN nomenclature?

International System for Human Cytogenomic Nomenclature — the standardized format for reporting karyotypes. Examples: 46,XX (normal female); 46,XY (normal male); 47,XX,+21 (Down syndrome female); 46,XY,t(9;22)(q34;q11.2) (CML — Philadelphia chromosome); 46,XX,del(5)(q31q33) (5q- syndrome). FISH results use 'ish' for metaphase or 'nuc ish' for interphase prefix. ISCN is updated periodically (2020, 2024) with new conventions for arrays and NGS.

What chromosomal abnormalities are essential for CG?

Constitutional: trisomy 21 (Down), 18 (Edwards), 13 (Patau); monosomy X (Turner 45,X); 47,XXY (Klinefelter); microdeletions (22q11.2 DiGeorge, 15q11-q13 Prader-Willi/Angelman, 7q11.23 Williams). Cancer: t(9;22) BCR-ABL1 (CML); t(15;17) PML-RARA (APL); t(8;21) RUNX1-RUNX1T1 (AML M2); inv(16) CBFB-MYH11 (AML); del(5q), del(7q), -7 (MDS); +12 (CLL); t(11;14) CCND1-IGH (mantle cell); t(8;14) MYC-IGH (Burkitt); t(14;18) IGH-BCL2 (FL).

How should I study for ASCP CG?

Plan 60-100 hours over 8-12 weeks. Focus heaviest on Cancer Cytogenetics (25%) and Constitutional Cytogenetics (25%) — together half the exam. Master ISCN 2024 nomenclature, the recurring chromosomal abnormalities by disease, FISH probe types and their applications, microarray interpretation, and mosaicism statistics (Hook's tables). Use ACMG technical standards as a reference.