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What is clinical cytogenetics? Congenital vs Aquired?
- The study of the relationship between human disease and chromosome alterations.
- Congenital: chromosome changes at birth (but not genetic). May result in mental retardation and abnormal physical appearance.
- Aquired: result of cancers or leukemias
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What are the four types of specimens commonly used in cytogenetic analysis? What are they used for (examples)?
- **studies require VIABLE cells capable of undergoing cell division
- Peripheral blood (NaHeparin): newborns with MCA, habitual abortion couples suspected of genetic abnormalities
- Amniotic fluid: prenatal genetic diagnosis (AMA, NTD, or history of chr abnormalities)
- Bone marrow: cancers and leukemias (chr abnormalities are nonrandom in these cases)
- Solid tissue: fetal tissues (products of conception, skin punch biopsies, solid tumors)
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What is the best mitotic stage to study chromosomes? Why?
- Prophase or metaphase
- Chromosome morphology is only visualized during mitotic division
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Describe the harvest procedure in analysis of cytogenetic specimens
- Colcemid: inactivates spindle formation, arresting cells at metaphase
- Hypotonic solution: causes WBCs to swell, lyses RBCs
- Fixative: Dehydrates/kills cells, hardens the nuclei
- Slide making: solution placed on slides, allowed to dry
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What are the various cytogenetic staining techniques with a brief description
- Pre-banding: very easy to make mistakes before any banding techniques were available
- G-banding (trypsin): the "standard" banding we use
- Fluorescence In-Situ Hybridization (FISH): DNA probe which hybridizes a specific region on a chromosome
- used to detect Trisomy/aneuploidy, marker chromosomes, deletions/duplications/translocations
- Spectral Karyotyping (SKY): each chromosome is stained a different color
- Cytogenomic Microarray (CMA): arrayed series of thousands of microscopic spots of DNA oligonucleotides (features)
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Describe a normal karyotype
- Arrangement of chromosomes from an individual arranged in pairs in descending order of size
- 1 to 22 + X/Y
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What are the autosomal and sex chromosome abnormalities with a brief description?
- Trisomy 21: down syndrome
- flat face, protruding tongue, cardiac defects, mental retardation
- Trisomy 18: Edward's syndrome
- Trisomy 13: patau syndrome
- cleft lip, polydactyly, severe mental retardation
- 45, X: Turner's syndrome
- no secondary sex characteristics, edema, gonadal dysgenesis
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Describe Burkit's lymphoma generally, morphologically, immunologically and cytogenetically.
- Aggressive B cell lymphoma
- Typically in children
- African presents with mass in jaw, associated with EB virus.
- American presents with abdominal mass.
- Morphologically: Monotonous proliferation of cells (cobblestone pattern)
- "Starry sky" appearance
- Deeply basophilic cytoplasm with multiple vacuoles
- Immunologically: CD19+ and CD10+
- Cytogenetically: 46,XY in marrow
- t(8;14) is characteristic
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Describe how CML and Mantle Cell Lymphoma can exist and be diagnosed in the same patient
- Mantle Cell Lymphoma caused by chemo
- 7 - 10% of NHL
- Characterized by t(11;14)
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