What laboratory technique is used to analyze the physical and chemical characteristics of cells or particles?

• A. Polymerase chain reaction (PCR)
• B. Karyotyping
• C. Immunohistochemistry
• D. Flow cytometry

Answer: (D)

Flow cytometry analyzes physical and chemical properties of cells or particles by passing them in a fluid stream through a laser and measuring light scattered as well as fluorescence from labeled antibodies or dyes. Forward scatter reflects cell size, side scatter indicates internal complexity, and fluorescence reveals specific molecules present on or in the cells. This combination lets you rapidly assess multiple characteristics at the single-cell level across many cells, and it can even sort cells based on those properties (FACS). In contrast, PCR looks at nucleic acids, karyotyping examines chromosome structure, and immunohistochemistry detects antigens in tissue sections rather than providing high-throughput multiparameter analysis of suspended cells.