Multiple del20q and 9pLOH events in colonies from 3 MPD patients. (A) The deleted region on chromosome 20q was mapped in individual colonies from patient p007 using 6 microsatellites distributed along chromosome 20q. T-cell DNA was used to define the 2 alleles for each informative microsatellite. The gray boxes mark the deleted region for each individual colony. del20q in colony no. 185 created a different haplotype than the deletion in colony no. 6 (marked by arrows), indicating that 2 del20q events occurred independently and affected the chromosome 20q of different parental origin. Furthermore, 4 different sizes of the del20q haplotype were detected when additional colonies were analyzed. The results from the mapping of the 9pLOH region are shown on the right side. The 9pLOH region is smaller in colony no. 185, as shown by the heterozygosity of D9S2148 in this colony. (B) Two separate del20q events affecting the chromosome 20q of different parental origin occurred in patient Vi102. (C) Two separate del20q events affecting the chromosome 20q of different parental origin occurred in patient Vi346. The chromatograms for the MPL-W515L mutation are shown for the 2 colonies analyzed.