Figure 1

Examples of DMFs. Panels A-C are Giemsa stained images of the Defective Mitotic Figures (DMFs) detected from human lymphocyte cultures following brief treatment with inhibitors of Topo II. As illustrated by these images, the key feature of DMFs is the differential condensation status among various chromosomes, resulting in the coexistence of condensed metaphase chromosomes and the uncondensed chromatin fibers within one mitotic figure. In normal mitotic figures all chromosomes condense at the same rate with no evidence of uncondensed chromatin appearing with condensed chromosomes. It should be noted that there are two types of DMFs classified as polarized and non-polarized. Fig 1A,1B shows condensed chromosomes and uncondensed chromatin or less condensed chromosomes in a polarized pattern. Fig 1C shows a non-polarized DMF. One biological application that can be derived from the morphology of DMFs is that in the abnormally condensed regions, chromatin fibers tangle with each other, which generates chromosomal breaks in later stages of the cell cycle when condensed chromosomes begin to segregate as observed in many cancer cells.