Translocation - use of cosmid probe

Human chromosomes at metaphase, highlighted by fluorescent probes that bind to specific base sequences on the DNA. This cell has a translocation between the X chromosome and a chromosome 13 (X;13). The cosmid probe from the XIST region (red) has not been disrupted by the Xq break point. The use of such probes can help to determine the break-points in the translocation. (See also B0000313C) Image by Dr John Crolla.