During FISH scoring for DiGeorge syndrome, the absence of an ARSA probe signal suggests what?

In the context of FISH (Fluorescence In Situ Hybridization) scoring for DiGeorge syndrome, the absence of an ARSA probe signal is indicative of a deletion in the ARSA region. DiGeorge syndrome is often associated with a microdeletion at chromosome 22q11.2, which can affect various genes, including the ARSA gene.

When performing a FISH analysis, probes are used to hybridize to specific regions of DNA. If a probe signal, such as that for ARSA, is absent, it is a powerful indication that there could be a deletion occurring in that specific region on one or both of the chromosomes being analyzed. Such deletions can contribute to the phenotypic manifestations of DiGeorge syndrome, making it a relevant finding in the diagnostic process.

Therefore, in this scenario, the absence of an ARSA probe signal leads to the conclusion that there is likely a deletion in the ARSA region, which aligns with the classic genetic alterations observed in patients with DiGeorge syndrome. The other choices may suggest alternative scenarios but do not directly connect the absence of the ARSA signal to the expected genetic interpretation associated with this syndrome.