Aging at the Level of DNA and Body Cells Programmed theories: Genes are “programmed” to cause changes resulting in aging. Telomeres: a type of DNA at the end of chromosomes that limit the number of times a cell can divide (usually 40-60) “random” damage theory: DNA is gradually damaged by spontaneous mutations or through external influences that cause mutations. The more damage, the more difficult cell repair and replacement becomes. Damage may also result in abnormal or cancerous cells Release of free radicals (naturally occurring, highly reactive chemicals that form in the presence of oxygen) may cause age-related DNA and cellular abnormalities
Aging at the Level of Organs and Tissues Cross-linkage theory: Over time, protein fibers that make up the body’s connective tissues form bonds (links) with one another. As these fibers cross one another, tissue becomes less elastic. Regular exercise and a vitamin-rich, low fat diet reduce cross linkage. Gradual failure of the endocrine system A decline in growth hormone is related to loss of muscle, increase of body fat and thinning of the skin Declines in immune system functioning Increase susceptibility to infectious and cardiovascular disease, and cancer.