Final answer:
A small deletion in the small arm of chromosome 5 causes Cri-du-chat syndrome, which leads to nervous system abnormalities, distinctive facial features, and a characteristic high-pitched cry in infants.
Step-by-step explanation:
Cri-du-chat syndrome is a genetic disorder caused by a specific chromosomal abnormality known as a "5p-" deletion, referring to the deletion of the short arm of chromosome 5. This syndrome manifests with a range of physical and intellectual abnormalities, and its name is derived from the distinctive high-pitched cry of affected infants, which resembles the mewing of a cat.
The chromosomal deletion in Cri-du-chat syndrome typically occurs during the formation of reproductive cells or early embryonic development. Individuals with this syndrome exhibit a characteristic cry, described as a high-pitched and cat-like sound, which is a key clinical feature observed in infancy. This cry often diminishes as the child grows older.
Apart from the distinctive cry, individuals with Cri-du-chat syndrome display a set of facial features that may include a small head (microcephaly), widely spaced eyes (hypertelorism), low-set ears, and a small jaw. These facial characteristics contribute to the recognizable appearance associated with the syndrome.
Nervous system abnormalities are prevalent in Cri-du-chat syndrome, leading to developmental delays and intellectual disabilities. Affected individuals may experience challenges in motor skills, speech development, and cognitive functions. Additionally, other physical abnormalities such as congenital heart defects and gastrointestinal issues may be present, contributing to the clinical complexity of the syndrome.
While there is no cure for Cri-du-chat syndrome, early intervention and supportive care can help manage symptoms and improve the quality of life for affected individuals. Genetic counseling is often recommended for families, providing information about the condition's genetic basis and assisting in understanding the potential recurrence risks in future pregnancies.