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Mitosis. Fluorescence micrograph of a cell during abnormal anaphase of mitosis (nuclear division). During mitosis two daughter nuclei are formed from one parent nucleus. This requires organisation of the chromosomes (blue) and mitotic spindles (red) to ensure that each cell retains an exact copy of the parent cell's genetic information. Usually at anaphase the two identical sister chromatids that make up a chromosome are pulled to opposite ends of the cell. However, in this cell the spindles are having trouble separating the chromatids. Abnormal mitosis can lead to cell abnormalities or cell death. (KEYSTONE/SCIENCE PHOTO LIBRARY/DR PAUL ANDREWS, UNIVERSITY OF DUNDEE/ SCIENCE PHOTO LIBRARY)