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 aware 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 or absence of the specific chromosomal change by using velocardiofacial syndrome-specific probes and a sample of the child's DNA. To which technique is the genetic counselor likely referring?

O recombination frequency-based mapping
O fluorescence in situ hybridization (FISH)
O sequence tagged site (STS) mapping
O restriction fragment length polymorphism (RFLP) analysis