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Fig. 4 | Stem Cell Research & Therapy

Fig. 4

From: Rejuvenation by cell reprogramming: a new horizon in gerontology

Fig. 4

The two theories at work. a According to the cumulative DNA damage theory, when a hypothetical 25-year-old human couple conceives a new individual, the zygote they conceived inherits the DNA damage of the parental germ cells. (Left enlarged panel) According to the theory, after each generation, DNA damage in the successive zygotes would be accumulated through inherited damage, causing species viability to decline progressively over the centuries, eventually driving them to extinction. (Main diagram) According to the epigenetic model, at the time of fertilization, all the epigenetic marks of parental aging are erased from the zygote’s genome by the reprogramming factors present in the cytoplasm, thus resetting its aging clock back to zero (b, left enlarged panel). Consequently, in each generation, the epigenetic clock of zygotes will restart from zero, thus allowing that complex animal species flourish and diversify over time (b, main diagram)

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