Aging is a common characteristic of multicellular eukaryotes.Copious hypotheses have been proposed to explain the mechanisms of aging, but no single theory is generally acceptable.In this review, we refine the RNA population gene activating model (Lv et al., 2003) based on existing reports as well as on our own latest findings.We propose the RNA population model as a genetic theory of aging.The new model can also be applied to differentiation and tumorigenesis and could explain the biological significance of non-coding DNA, RNA, and repetitive sequence DNA.We provide evidence from the literature as well as from our own findings for the roles of repetitive sequences in gene activation.In addition, we predict several phenomena related to aging and differentiation based on this model.