Final answer:
Chromosomes have a short arm designated by the letter p and a long arm designated by the letter q in a human karyotype.
Step-by-step explanation:
In a human karyotype, chromosomes have a short arm designated by the letter p and a long arm designated by the letter q. The short arm is abbreviated as p because it stands for "petite", while the long arm is abbreviated as q because it follows p alphabetically. Each arm is further subdivided and denoted by a number.