Micronucleus Test Flashcards
DNA fragment that is separated from the main nucleus and has originated from a chromosome or fragment of a chromosome that fail to be included into one of the daughter nuclei during cell division
Micronucleus / Micronuclei (Howell-Jolly bodies)
Proponent of Howell-Jolly bodies
William Howell & Justin Jolly
Micronucleus / Micronuclei is an extracellular biomarker for _______________, which is used to assess toxicity
Chromosomal damage
Micronucleus / Micronuclei are typically round with a diameter of about ________ to _______ of the erythrocytes. They are almost __________-shaped (clue: nut)
1/20; 1/5; almond
This stage of cell division is where chromosomal breaks happen
Metaphase
This stage of cell division is where chromatin distribution disturbances happen
Anaphase
This stage of cell division is where the displaced chromatin are excluded from the nuclei of the daughter cells
Telophase
These are chromosome-breaking substances in the bone marrow and spleen
Clastogen
This substance, in the bone marrow or spleen, leads to loss of whole chromosome activity
Aneugen
Identification (Clastogen /Aneugen)
The pathway of this substance is: Break → Lagging Break → Acentric MN
Clastogen
Identication (Clastogen /Aneugen)
The pathway of this substance is: Spindle dysfunction → Lagging chromosome → Centric MN
Aneugen
Endpoints of genetic damage
Gene mutation, Clastrogenicity, Aneuploidy
Point mutations or deletions/insertions that affect single or blocks of genes. This happens during the replication stage of central dogma
Gene mutation
This endpoint results in structural chromosome changes
Clastrogenicity
The occurrence of one or more extra or missing chromosomes, leading to unbalanced chromosome complement
Aneuploidy
Micronucleus Test is an _________ toxicity study developed by ________ and co-workers in 1975.
In vivo; Schmid
Used to screen compounds for genotoxicity caused by clastogens (chromosome-breaking) or aneugens (loss of whole chromosome activity) by detecting micronuclei.
Micronucleus Test
Micronucleus Test Principle: When a bone marrow __________ develops into a _________ erythrocyte, the main nucleus is _________; micronuclei that have been formed may remain behind in the otherwise ____________________
Erythroblast; polychromatic; extruded; enucleated cytoplasm
Immature erythrocytes: _________; Mature erythrocytes: nucleus disappears
Nucleated
T/F: Micronuclei are found in a variety of different marrow cells (myeloblast, myelocytes, erythroblasts, erythrocytes)
True
T/F: Majority of micronuclei are found in monochromatic (immature) erythrocytes
False. Majority are found in polychromatic (immature) erythrocytes
Identify the Giemsa stain color
_______: immature; Pinkish or orange: mature
Blue
Test animals in Micronucleus Test
T/F: male or female rodents may be used
Fill in the blanks
- ______ mice or rats
- Ideally _________ weeks old at the start of treatment
- Weight variation should not exceed +/- _____% of mean weight
True
Swiss; 6-10; 20
Micronucleus Test substances
Three dose levels usually ____, ____, ____, of the LD50
1/8; 1/4; 1/2
T/F: in micronucleus test substances, solids must be dosed directly or diluted prior to dosing. Liquids must be dissolved in appropriate solvent.
False
Solid – must be dissolved in appropriate solvent
Liquid – may be dosed directly or diluted prior to dosing
Substances that produce a detectable increase in micronucleus frequency
Positive control
These are positive control substances that are used as aneugens
Colchicine and vinblastine
T/F: Colchicine and vinblastine, as aneugens, cause loss of chromosomal activity. They are microtubule synthesis inhibitors that cause metaphase arrest
True
These are substances, solvents or vehicles used in administering the test chemical
Negative control (e.g. NSS)
T/F: The administration of the test substance is administered IP, IM, PO twice, 48 hours before and 12 hours before the animals are sacrificed)
False. Administered IP, IM, PO twice (30 hours before and 6 hours before the animals are sacrificed)
In the preparation of the bone marrow smear, both _______ of freshly sacrificed animal wholly cut through ______ and ______.
femurs; pelvis; tibia
In the preparation of the bone marrow smear, insert a 1mL syringe through the cavity of the femur and submerge in the ____________________ contained in a 5mL centrifuge tube
fetal bovine serum
T/F: In the preparation of the bone marrow smear, the insides of the femur must appear reddish after aspirating and flushing using the syringe
False. Whitish
In the preparation of the bone marrow smear, the suspension must be spread thinly with the aide of the cover slip angled at _____ degrees. Then, it must be air dried for at least ____ hours
45; 24
In staining, what is the ratio of the diluted Giemsa stain?
1:6
How many polychromatic erythrocytes should be screened for micronucleated polychromatic erythrocytes?
1000
T/F: Do not store the multinucleated cells and cells undergoing apoptosis
True
Why is Andre Martin E. Marapao so very very very handsome
because he is perfect
