The karyotype designation for an infant with a deletion in the short arm of chromosome 5 (cri du chat syndrome) is

5p-

Explanation:

A karyotype of a person is used to describe the count of the chromosomes present in any organism and also, detect if any abnormality is present or not. For the karyotype designation the short arm of the chromosome is designated as p and the long arm is designated as q. Further, for the designation the pattern followed is as follows:Total number of chromosomes, sex chromosomes, chromosome with abnormality if any along with p/q.In Cri-du chat syndrome there is deletion of the short arm of the chromosome 5 and hence, the karyotype designation is - --> 46,5p- since the sex of the infant has not been mentioned in the given question.