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. 2001 Jul 17;98(15):8196–8202. doi: 10.1073/pnas.121008898

Figure 1.

Figure 1

Visualization of sister chromatid exchanges during genomic replication in human cells. By growing cells in the presence of the thymine analog, 5-BrUra, for two generations, sister chromatids can be differentiated by using Giemsa stain. Exchanges between sister chromatids can then be observed directly by the staining pattern. (A) In normal human cells, semiconservative replication is maintained and few, if any, exchanges are observed. (B) However, cells from patients with the cancer-prone disorder of Bloom's syndrome lack a RecQ homolog that allows recombination to occur more frequently between sister chromatids. (C) Sister chromatid exchanges can also be induced in normal cells by treatment with carcinogenic agents such as MMS. [Photos taken from Sister Chromatid Exchange, S. Wolff, ed. (Copyright 1982; this material is used by permission of John Wiley & Sons, Inc.; ref. 7) and from The Chromosomes in Human Cancer and Leukemia, A. A. Sandberg (Copyright 1990; McGraw–Hill Companies, Inc.; ref. 62).]