AP BIOLOGY

Detailed explanation-1: -Cellular senescence refers to a state of stable cell cycle arrest in which proliferating cells become resistant to growth-promoting stimuli, typically in response to DNA damage.

Detailed explanation-2: -Although senescence plays physiological roles during normal development and it is needed for tissue homeostasis, senescence constitutes a stress response triggered by insults associated with aging such as genomic instability and telomere attrition, which are primary aging hallmarks themselves.

Detailed explanation-3: -Characteristics of senescent cells Senescent cells are characterised by flattened and enlarged morphology. They exhibit several molecular markers, including telomere-dysfunction-induced foci, senescence-associated heterochromatin foci (SAHF), lipofuscin granules, DNA scars, altered gene expression (5, 7).

Detailed explanation-4: -As the aging immune system becomes less efficient, senescent cells accumulate and taint healthy cells. This can affect a person’s ability to withstand stress or illness; recuperate from injuries; and learn new things, since senescent cells in the brain can degrade cognitive functions.