Metaphase spread of a cell line showing a ring chromosome (R) and several sister chromatid exchanges (SCEs), some of which are indicated by arrows. Original figure legend: <i>Metaphase chromosome spread from an induced cell transfected with GFP-ΔC1 BLM. A large ring chromosome is shown at the top of the spread. The SCEs are visualized with acridine orange staining.</i>
Victor Yankiwski, James P Noonan and Norma F Neff
CC BY 2.0
<p>The C-terminal domain of the Bloom syndrome DNA helicase is essential for genomic stability. Figure 6C <a rel="nofollow" class="external text" href="http://www.biomedcentral.com/1471-2121/2/11">BMC Cell Biology 2001, 2:11</a>. DOI:10.1186/1471-2121-2-11. 
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The 'R' and the arrows are not part of the original image but were added by the uploader.