SCIENCE NEWS DIGEST FOR PHYSICIANS AND SCIENTISTS
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Anaphase is initiated by the separation of the sister chromatids (see figure below). This event is irreversible and commits the cell to the completion of cell cycle. There are checkpoint controlling mechanisms that regulate the mitosis. At least six signals have been so far identified in the yeast that participate in this checkpoint mechanism. They include MAD1 (mitotic arrest-deficient), MAD2, MAD3, BUB1 (budding uninhibited by benzimidazole) , BUB2, BUB3. Chen et al have found the Xenopus and Li and Benezra have identified the human homolog of the MAD2. Li and Benezra examined the expression of the human or homosapiens MAD2 (hsMAD2) in the T47D, human breast carcinoma cell line. These cells showed a reduced expression of hsMAD2. In addition, when treated with nocodazole (a mitotic cell inhibitor), these cells failed to arrest in mitosis. Based on these findings, it was suggested that the defect in the expression of the hsMAD2 may contribute to the sensitivity of certain human tumors to the treatment with the mitotic spindle inhibitors. REFERENCES
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| MITOSIS | |||||||||||||
| Preparation for mitosis | Prophase | Metaphase | Anaphase | Telophase | Interphase | Animated mitosis | |||||||
| Chromosomes duplicate | The duplicated chromosomes line up in a single file | Chromatids and therefore the centreomers divide | The nuclei divide | DNA synthesis halts (Cell enters G0 phase) | The Source: Dept of biology: Yale University G1 phase | S phase G2 phase 
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Chen, R.-H.; Waters, J. C.; Salmon, E. D.; Murray, A. W. :
Association of spindle assembly checkpoint component XMAD2 with unattached kinetochores.