Which of the following procedures is used as a routine technique for karyotyping using light microscopy?

Giemsa stain is the most commonly used staining method that allow identification of each individual chromosome, on the basis of a distinctive and reliable pattern of alternate light and dark bands along the length of the chromosome. Since giemsa stain is used, the procedure is called G banding. Ref: Robbins Pathologic Basis of Disease, 6th Edition, Pages 165-6