Answer to Question 1
Answer: C
Answer to Question 2
Answer: Genetically programmed aging proposes the existence of aging genes that control biological changes, such as menopause, efficiency of gross-motor skills, 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. And greater similarity exists in the lifespans of identical than fraternal twins. But the heritability of longevity is low to moderate. 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 telomereslocated at the ends of chromosomes, serving as a cap to protect the ends from destructionshortens . Eventually, so little remains that the cells no longer duplicate at all. 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 shorteningpowerful biological evidence that certain life circumstances compromise longevity.
Replicative senescence in hematopoietic development
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Chewing & Swallowing: Food Processing Begins
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