Describe the theory of biological aging that emphasizes the programmed effects of specific genes

Question

What will be an ideal response?

Answer 1

Genetically programmed aging proposes the existence of "aging genes" that control certain biological changes, such as menopause, gray hair, and deterioration of body cells. The theory receives some support from kinship studies indicating that longevity is a family trait. People whose parents had long lives tend to live longer themselves. But the heritability of longevity is modest. Rather than inheriting longevity directly, people probably inherit risk and protective factors, which influence their chances of dying earlier or later. The strongest evidence for the existence of "aging genes" comes from research showing that human cells allowed to divide in the laboratory have a lifespan of 50 divisions, plus or minus 10. With each duplication, a special type of DNA called telomeres—located at the ends of chromosomes, serving as a "cap" to protect the ends from destruction—shortens. Eventually, so little remains that the cells no longer duplicate. Telomere shortening acts as a brake against somatic mutations, which become more likely as cells duplicate. But an increase in the number of senescent cells (ones with short telomeres) also contributes to age-related disease, loss of function, and earlier mortality. Researchers have begun to identify health behaviors and psychological states that accelerate telomere shortening—powerful biological evidence that certain life circumstances compromise longevity.