- What does the Ames test detect?
A) Protein synthesis inhibition
B) DNA strand breaks
C) Point and frame-shift mutations in bacteria
D) Hormonal disruption in rodents
C - The Ames test detects point mutations (TA100/TA1535) and frame-shift mutations (TA98/TA1537/TA1538) in Salmonella.
- What is the function of microsomes (S9) in the Ames test?
A) Provide nutrients for bacterial growth
B) Detect direct-acting carcinogens
C) Mimic mammalian metabolism to activate procarcinogens
D) Prevent bacterial mutations
C - Microsomes (S9 mix) provide liver enzymes to metabolically activate procarcinogens into their mutagenic form.
- What gene is used in the Chinese Hamster Ovary (CHO) test?
A) Thymidine kinase
B) P53
C) HGPRT
D) Ras
C - HGPRT (hypoxanthine-guanine phosphoribosyl transferase) is used to detect mutations in the CHO cell test.
- Which in-vivo gene mutation assay uses β-galactosidase as a reporter?
A) Pig-a assay
B) Big Blue mouse
C) MutaMouse
D) CHO test
C - MutaMouse assay uses β-galactosidase reporter to detect mutations in every cell of the mouse.
- What is the Pig-a gene mutation assay used to detect?
A) Chromosomal duplications
B) Changes in liver enzymes
C) Loss of GPI-anchored proteins on RBCs
D) DNA methylation status
C - Pig-a assay detects mutations in the gene required for GPI-anchor protein expression on red blood cells.
- What does the micronucleus test detect?
A) Protein aggregation
B) DNA replication speed
C) Chromosomal damage during cell division
D) Immune cell proliferation
C - The micronucleus test detects chromosomal fragments or whole chromosomes not incorporated into daughter nuclei.
- What is the primary purpose of the comet assay?
A) Assess apoptosis rates
B) Detect oxidative stress proteins
C) Measure DNA strand breaks at the single cell level
D) Identify RNA mutations
C - The comet assay visualizes and quantifies DNA strand breaks in individual cells using electrophoresis.
- What is the duration of a chronic carcinogenicity bioassay?
A) 1 week
B) 30 days
C) 90 days
D) 2 years
D - Chronic bioassays run for 2 years and are considered the gold standard for carcinogenicity testing.
- What is MTD in chronic bioassays?
A) Minimum toxic dose
B) Most tolerable dilution
C) Maximum tolerable dose with no toxicity in 90 days
D) Median threshold dose
C - MTD is the maximum dose that does not cause overt toxicity in a 90-day study, used for setting top dose levels.
- What promoter is commonly used in skin carcinogenicity models?
A) Diethylstilbestrol
B) Phenobarbital
C) TPA (12-O-tetradecanoylphorbol-13-acetate)
D) Clofibrate
C - TPA is a tumor promoter used in skin cancer models for evaluating initiation and promotion stages.
- What staining marker is used to observe pre-neoplastic foci in liver assays?
A) Cytochrome P450
B) GSH-P (glutathione transferase pi)
C) β-galactosidase
D) Histone deacetylase
B - GSH-P (glutathione transferase pi) is a biomarker for early liver lesions in promotion studies.
- Which genetically altered mouse strains are used in carcinogenicity testing?
A) MutaMouse, Big Blue, Pig-a
B) TgAC, rasH2, P53
C) CAR, AhR, EGFR
D) B6C3F1, F344, BALB/c
B - Transgenic mice such as TgAC, rasH2, and P53 knockout are used in rapid carcinogenicity screening.
- Which organization classifies human carcinogens into categories?
A) WHO
B) FDA
C) IARC (International Agency for Research on Cancer)
D) EPA
C - IARC is responsible for evaluating carcinogenic risks and classifying agents into Group 1–4 categories.
- What is a characteristic of IARC Group 1 agents?
A) Not carcinogenic to humans
B) Possibly carcinogenic to animals only
C) Carcinogenic to humans based on sufficient evidence
D) Requires further study before classification
C - Group 1 IARC agents have sufficient evidence to be considered carcinogenic to humans.
