7.3: Mitosis
- Page ID
- 4847
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This image provides a graphic illustration of the problem. It shows a bit (no more than 3%) of the single molecule of DNA released from a single human chromosome. (The chromosome was treated to remove its histones). Remembering that this is 3% of the DNA of only one of the 46 chromosomes in the human diploid cell, you can appreciate the problem faced by the cell of how to separate without error these great lengths of DNA without creating horrible tangles.
The solution to this problem is:
- Duplicate each chromosome during the S phase of the cell cycle.
- This produces dyads, each made up of 2 identical sister chromatids. These are held together by a ring of proteins called cohesin.
- Condense the chromosomes into a compact form. This requires ATP and protein complexes called condensins.
- Separate the sister chromatids and
- Distribute these equally between the two daughter cells.
