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15 - Cell cycle control, apoptosis, and ageing

Published online by Cambridge University Press:  01 June 2011

Richard J. Epstein
Affiliation:
University of Singapore
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Summary

Most cells grow throughout their lifespan. Intestinal crypt cells or bone marrow precursors proliferate continuously, for example, whereas hepatocytes divide intermittently and spend the intervening periods at rest. In contrast, normal adult neurons do not divide to any significant extent. Mature red blood cells and platelets can also be characterized as postmitotic, since neither contain nuclei. Such cells are said to be terminally differentiated. The framework used for considering how cells make decisions about growth, differentiation, senescence, and death is termed the cell cycle.

Cell cycle control genes

Chromosomes separate and rejoin in a cyclical fashion

As detailed earlier, proliferating cells contain chromosomes that undergo recurring structural changes termed interphase, prophase, metaphase, anaphase, and telophase. The last four (mitotic) phases of this chromosomal cycle account for only a small percentage of the time involved for a cell to reproduce. Mitosis lasts about an hour in humans, whereas the time between mitoses (interphase) lasts 18–24 hours. In contrast, certain bacteria spend as little as ten minutes between successive divisions.

Though microscopically unremarkable, the interphase period of chromosomal dispersion conceals many of the key molecular events that define the cell cycle. The cell (division) cycle represents a set of controls to ensure that one round of division follows one round of DNA replication just as one round of DNA replication follows one of cell division.

Type
Chapter
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Human Molecular Biology
An Introduction to the Molecular Basis of Health and Disease
, pp. 356 - 388
Publisher: Cambridge University Press
Print publication year: 2002

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