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Cellular clock | Cause | Molecular readout |
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Error-catastrophe theories | | |
Somatic mutation accumulation | Metabolism/oxygen free radicals | Altered protein function, DNA damage |
Mitochondrial DNA mutation | Oxygen free radicals | Altered mitochondrial function |
Posttranslational modification of proteins | Oxidation, glycosylation, acetylation, methylation, and so forth | Altered function of proteins |
Altered proteolysis | Errors in proteolysis machinery | Accumulation non functional proteins |
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Deterministic theories | | |
Telomere shortening | no replication of the telomere ends | DNA damage, exposure ends of telomeres, Liberation regulatory proteins, and so forth |
Changes in heterochromatin domains | | changes in transcription |
Changes in DNA methylation | | changes in transcription |
Codon restriction | Switching codon preferences in early development, restrict availability later In life | Altered protein synthesis |
Terminal differentiation | Senescence is a form of terminal di- fferentiation genetically controlled | |
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