ASCP MLS Molecular Diagnostics Exam with Questions and Answers

ASCP MLS Molecular Diagnostics Exam with Questions and Answers Which type of specimen would be unsuitable for FISH analysis? A. Paraffin-embedded tissue B. Cells with chromosomes in metaphase C. Cells with chromosomes in interphase D. A cell suspension containing maternal and fetal blood ANSWER D. FISH can be used with almost any type of cell preparation, including frozen sections, formalin fixed tissues, embedded tissues, and cell suspensions such as those derived from amniotic fluid or chorionic villus sampling provided they are pure. Cells in suspension can be dropped onto glass slides or concentrated using a cytocentrifuge before processing. However, a mixture of cells from different individuals is inappropriate because the probe cannot distinguish between sources such as fetal and maternal cells. FISH can distinguish each of the following chromosomal abnormalities except: A. Aneuploidy B. Translocation C. Deletion D. Trinucleotide repeats ANSWER D. FISH can detect conditions that are associated with structural chromosomal abnormalities and an abnormal number of chromosomes (aneuploidy). A screening test for aneuploidy employs probes labeled with different fluorescent dyes that simultaneously detect trisomy 21, 18, and 13 and the X and Y chromosomes. Deletions cause the absence of a fluorescent signal when expected, and microdeletions such as those that occur on the short arm of chromosome 5 in cri du chat syndrome can be detected by FISH. Translocations cause two different FISH probes to bind to the same chromosome. Such probes are used to identify IgH gene translocations such as t(11:14) in multiple myeloma that are of prognostic value. However, trinucleotide repeats, repetitive sequences of the same three base pairs, are not detected by FISH. This is associated with fragile X syndrome, myotonic dystrophy, Huntington's disease, and other genetic diseases. PCR or Southern blotting are used for detection of these repeats, depending upon their number. In microarray and macroarray analysis, which molecules are labeled? A. The immobilized DNA molecules B. The sample DNA C. Both target and sample molecules D. The substrate matrix ANSWER B. An array is an organized arrangement of known molecules (either DNA or proteins for proteomic array analysis). DNA arrays are used primarily for studying gene expression and single nucleotide polymorphisms. Commercially prepared arrays use short synthetic oligonucleotides (12-36 bases) of