Karyotyping

Karyotyping is a method for studying the chromosomes of an organizm. Karyotype is a standardised arrangement of metaphasic chromosomes that have been photographed and arranged in the order of decreasing length. The cell division is arrested in metaphase by using inhibitors of spindle formation like colchicine and stained. Different techniques for staining are available to identify the individual chromosomes eg. staining with Giemsa (G bandng). G banding shows alternating dark and light bands in the chromosome. Numerical chromosomal abnormalities such as trisomy 21 (Down syndrome) can be easily identified using karyotyping. One disadvantage is that karyotyping can be applied only to cells which divide or can be induced to divide in vitro.