\"Suppose that a mother seeks genetic counseling because she is concerned that h
ID: 164947 • Letter: #
Question
"Suppose that a mother seeks genetic counseling because she is concerned that her child may have velocardiofacial syndrome, a syndrome that can result in symptoms such as a cleft palate and heart defects. The genetic counselor is ware that this disease is caused only by a small deletion in chromosome 22q11.2, that traditional karyotyping often overlooks. Consequently, the genetic counselor informs the mother that a cost-effective test will be conducted to visually detect the presence of absence of the specific chromosomal change by using velocardiofacial syndrome-specific probes and a sample of the child's DNA. To which of the following techniques is the genetic counselor referring?" Fluorescence in situ hybridization (FISH) Restriction fragment length polymorphism (RFLP) analysis Sequence tagged site (STS) mapping Linkage mappingExplanation / Answer
Answer: (a) Fluorescence in situ hybridization (FISH)
Velocardiofacial syndrome is currently the most common microdeletion known, and is caused by deletions of 3 Mb at chromosome 22q11.
FISH studies uses probes such as N25 or TUPLE1 within the most commonly deleted region, and have allowed clinical laboratories to identify patients with submicroscopic 22q11.2 deletions.
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