An evolutionary review of XXXX telomere biology: the thrifty telomere hypothesis and notes on potential adaptive paternal effects.

@entity1 @entity5 @entity3207 @entity281 @entity1240
Telomeres, repetitive DNA sequences found at the ends of linear chromosomes, play a role in regulating cellular proliferation, and shorten with increasing age in proliferating @entity1 tissues. The rate of age-related shortening of telomeres is highest early in life and decreases with age. @entity3207 are thought to limit the proliferation of cells and are associated with increased morbidity and mortality. Although natural selection is widely assumed to operate against long telomeres because they entail increased @entity5 risk, the evidence for this is mixed. Instead, here it is proposed that telomere length is primarily limited by energetic constraints. Cell proliferation is energetically expensive, so shorter telomeres should lead to a thrifty phenotype. Shorter telomeres are proposed to restrain adaptive immunity as an energy saving mechanism. Such a limited immune system, however, might also result in @entity281 , inflammatory stress, @entity1240 , and death--a more "disposable soma." With an increased reproductive lifespan, the fitness costs of @entity1240 are higher and longer telomeres will be favored by selection. Telomeres exhibit a paternal effect whereby the offspring of older fathers have longer telomeres due to increased telomere lengths of sperm with age. This paternal effect is proposed to be an adaptive signal of the expected age of male reproduction in the environment offspring are born into. The offspring of lineages of older fathers will tend to have longer, and thereby less thrifty, telomeres, better preparing them for an environment with higher expected ages at reproduction.
