21. Cytogenetics/Molecular Diagnostics

Question 1

Down Syndrome

Answer 1

• trisomy 21
• can be caused by additional chromosome or translocations
• increases the risk for leukemia (ALL, AMKL, and transient leukemias)

Question 2

Fluorescence In Situ Hybridization

Answer 2

• molecular testing
• hybridize to chromosomes.We want it to bind to the same locus the probe was taken from.
• using fish allows us to look at a very specific type of translocation whereas karyotyping would take longer to get results.
• can also be used for bone marrow transplants. To compare donor cells to patient’s disease cells.
• can be used to diagnose APL: Acute promyelocytic leukemia t(15;17)
• more rapid results than karyotype
  - Ease of monitoring patients
  - Increased statistical significance of results (500 cells vs 20 cells)

Question 3

Microarray

Answer 3

- can be used to detect 
multiple mutations on different 
chromosomes with a single assay. 
-Ex: CML t(9;22)
- A single genomic assay
- Information may not be interpretable because not all genes have been mapped/identified

Question 4

Hereditary Hemochromatosis

Answer 4

• direct mutational analysis
  ‹- Mutations: C282Y, H63D
• carrier frequency is very high
• males are more commonly affected because women have a regular monthly bleeding to release extra iron from their system.
• PCR + gel electrophoresis can confirm diagnosis or show that the patient is at an increased risk for hereditary hemochromatosis.
• Identify at risk individuals earlier in life
  ‹- Reduce need for liver biopsy
  ‹- Get a direct diagnosis of disorder