Cytogenetics Review Questions

List the three broad categories of clinical indications for chromosomal analysis.
Prenatal, Constitutional, Cancer/Acquired

List 5 prenatal indications for cytogenetics analysis.
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Which family members should have chromosomal analysis?
Both parents of a child with structural chromosome rearrangement, deletion, duplication 2) all family members at risk of having a chromosome rearrangement

What are the indications for chromosomal analysis of products of conception?
1)Abortuses (missed abortions) of unknown reason, 2)Malformed stillbirths, 3)Stillbirth of undetermined etiology

Compare amniocentesis and chorionic villus sampling with regards to gestational age, complication rate, turn around time, and false results

What are the clinical indications for tissue sampling instead of blood for cytogenetic analysis?
1)Suspicion of chromosomal mosaicism, 2) blood is not available (e.g. POC), 3) surgical or post-mortem tissue.

List 8 standard techniques for cytogenetics analysis.
1) Geimsa / G-Banding, 2) Quinacrin / Q-banding 3) Reverse / R-banding, 4)Centromere / C-banding, 5)NOR staining (nucleolus organizer regions), 6)DAPI staining, 7) Chromosomal breakage, 8) Sister chromatid Exchange (SCE)

List 5 Molecular cytogenetics techniques.
1)FISH (flourescence in situ hybridization), 2) Multi-colour FISH, 3) SKY (spectral karyotyping), 4) CGH (comparative genomic hybridization), 5) CGH array, 6) S-ISH, 7) D-ISH

What is g-banding?
Chromosomes are treated with trypsine and then stained with Geimsa (or wrights) which darkly stains the AT rich regions (heterochromatin), and lightly stains the GC rich regions of the chromosome.

Outline the general procedure for cytogenetics study.

1) cell culture at 37C 5%CO2 in medium (dividing and stimulation), 2) Chromosome elongation Thymidine BrdU, 3) Metaphase arrest with Colcemide, 4) Cell swelling with hypotonic KCl,* Hardening with acetic acid* 5) Fixation with Cournay's (Methanol: Acetic acid, 3:1), 6) Slide making (chromosome spread with ideal temperature and humidity), 7) Slide aging (air dry slide warmer), 8)Staining (G, Q, C, R-banding), 8) Molecular cytogenetic technique (FISH, multi-FISH, CGH, SKY, array CGH).

Broadly what at the three main morphological groups of chromosomes?
Metacentric, acrocentric, submetacentric.

What are the 4 minimum items included in a standard banding nomenclature?
1. Chromosome number, 2) short or long arm, 3) region on that arm, 4) band number within that region

What are the clinical indications for an individual to have chromosomal analysis?
1)suspected classic chromosome syndrome, 2) Mental retardation of undetermined etiology, 3) dysmophic features, 4) multiple congenital abnormalities, 5) abnormalities of sexual development, 6) ambiguous genitalia, 7)pubertal failure, 8)abnormalities of growth, 9) certain types of malignancies.

What is q-banding?
Chromosomes are prepared with quinacrine which produces flourescent bands in the AT rich regions, particularly useful in identifying polymorphisms on the acrocentric chromosomes ( ) and the Y chromosome.

What is R-banding?
Darkly stains the GC rich regions of the chromosome (Euchromatin), aka Reverse-banding, and is used to detect subtle deletions or rearrangements that may not be detected by Q or G banding.

What is C-banding?
C-Banding stains the constituitive heterochromatin that is localized to the pericentromeric regions of all chromosomes and on the distal long arm of Y. Used to identify pericentric inversions and polymorphisms in centromeric regions of 1,9,16, and Yq, as well as confirming translocations of Y

What is NOR?
NOR is a silver staining procedure which stains the nucleolus organizer regions of satellited chromosomes (used to study the size of stalks and satellites in the acrocentric chromosomes)

List the metacentric chromosomes.

List the submetacentric chromosomes.

List the acrocentric chromosomes.

What is Bloom syndrome?
Bloom syndrome is a rare genetic disorder

What is SCE (Sister chromatid exchange?
SCE (sister chromatid exchange) is the interchange of homologous segments between two chromatids of one chromosome, grow the cells under special conditions to produce a differential staining of sister chromatids.