Karyotyping involves the microscopic examination of the chromosomes to investigate the total number and structure of the chromosomes. It is also known as chromosome analysis. Cells are obtained from an individual and are viewed during metaphase, a stage in cell division when our chromosomes are condensed. The chromosomes are stained with a dye (Giemsa), resulting in a banding pattern of light and dark stripes, known as G-banding. The patterns are specific, allowing us to identify each chromosome.

This test can detect loss or gain of material in any region of any chromosome as well as both balanced and unbalanced structural rearrangements such as translocations and inversions. As this test examines the chromosomes microscopically, the level of detail is limited by the resolution of the microscope and imbalances of ~ 5 Mb or greater can be detected.

Living cells are required for cell culture to produce the chromosome preparations hence frozen or fixed material cannot be processed.