Cri du Chat Syndrome

A 6-month-old female infant is brought to the pediatric clinic with a history of a distinctive high-pitched, mewing cry since birth. On examination, she has microcephaly, round facies with hypertelorism, epicanthal folds, micrognathia, and hypotonia. Karyotype analysis reveals a terminal deletion of chromosome 5. The structure marked **B** in the diagram represents the chromosomal abnormality responsible for this clinical presentation. Which of the following is the MOST characteristic feature that gives this syndrome its eponymous name?