16 Mitosis I - BME 418, Quantitative Cell Biology #17:...

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BME 418, Quantitative Cell Biology Alan J. Hunt #17: Mitosis I Mitosis The basic element of life is the cell, and all cells are produced by division of progenitors. The critical challenge during division is ensuring that both daughter cells receive a full complement of the materials necessary to sustain life. For plentiful components this is relatively simple; if a cell divides into two daughters of roughly equal size statistics will assure that each daughter receives sufficient material. Components that exist in limited copy numbers must be carefully segregated between daughter cells. This applies most obviously to the genetic material: - Low copy number. - Missing sequences cannot be replaced. - Critical need for complete genetic information: failure = death or disease. For prokaryotes segregation of the genetic material is relatively simple since all sequences are contained on a single circular DNA molecule. Scanning and light (inset) micrographs of condensed mitotic chromosomes.
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BME 418, Quantitative Cell Biology Alan J. Hunt In eucaryotes, segregation of DNA is more complex since the DNA is distributed between multiple different packages, the chromosomes (23 pairs in humans). Chromosomal material, chromatin, is normally diffuse within the nucleus, but condenses in preparation for cell division. Chromosome structure: - Two identical sister chromatids, bound at sequences of DNA called centromeres. - Centromeres located at primary constriction - A complicated structure called the kinetochore is also located at the primary constriction. The kinetochore is made up of both chromosomal DNA and proteins, and plays a central role in chromosome movements. During eukaryotic cell division each sister chromatid must be segregated into
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This note was uploaded on 09/06/2008 for the course BIOMEDE 418 taught by Professor Hunt during the Winter '08 term at University of Michigan.

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16 Mitosis I - BME 418, Quantitative Cell Biology #17:...

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