Flow karyotyping is a method of analyzing and characterizing the number, sizes and shapes of the entire set of metaphase chromosomes of a cell, using a flow cytometer called fluorescence activated chromosome sorter (FACS). Karyotype analysis is an important laboratory diagnostic procedure in cancer genetics, prenatal diagnosis, hematological disorders, and many other diseases.

Chromosomes are not visible in non-dividing cells, even with the aid of histological stain for DNA and electron microscopy. These chromosomes will condense and become visible at the metaphase stages of cell division during meiosis and mitosis. Cytogenetic and karyotyping analyses have, therefore, been done with condensed metaphase chromosomes obtained from dividing cells. The cells that reach mitosis have already progressed through the S phase of the cell cycle, during which DNA replication takes place. The condensed metaphase chromosomes thus obtained are duplicated structures; each chromosome consists of two sister chromatids that are...