A Cri-du-chat patient typically has which type of chromosome abnormality?

The correct answer reflects the typical chromosomal abnormality associated with Cri-du-chat syndrome, which is characterized by the deletion of a portion of the short arm of chromosome 5. Specifically, patients with this syndrome usually have a structural abnormality represented as 46,XY,del(5p), indicating a deletion on the short arm of chromosome 5.

Option A refers to a ring chromosome formation, r(5)(p15.1q35), which is not the standard chromosomal abnormality linked to Cri-du-chat. The syndrome is most accurately identified by the deletion notation, where the loss of genetic material leads to the phenotypic features characteristic of the disorder, including the distinct cry from which the syndrome derives its name.

The other choices represent different types of chromosomal abnormalities: translocations and ring formations that do not correlate with the clinical presentation of Cri-du-chat syndrome. Therefore, the most faithful representation of the genetic basis for Cri-du-chat syndrome in this context is the deletion on chromosome 5.