Representative example demonstrating clonality in various subpopulations of cells in patients with MDS.

(A) LOH (D5S471). (B) X-chromosome activation. Two peaks represent the 2 alleles. Loss of one peak (or significant reduction in its intensity) represents a loss of an allele. In the X-chromosome analysis, clonality is present when one peak disappears after digestion with the restriction enzyme Hpa1 because of lack of amplification products caused by the enzymatic digestion.