Final answer:
Chromosomes are usually photographed during the metaphase stage of mitosis in the preparation of a karyotype.
Step-by-step explanation:
Chromosomes are usually photographed during the metaphase stage of mitosis in the preparation of a karyotype. At this stage, the chromosomes are lined up at the metaphase plate, making them easily visible and distinguishable. The metaphase stage is characterized by the attachment of the chromosomes to the mitotic spindle fibers, which helps arrange them in an orderly manner.