3Aging 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 cellsRelease of free radicals (naturally occurring, highly reactive chemicals that form in the presence of oxygen) may cause age-related DNA and cellular abnormalitiesBiological aging results from a combination of influences. Heritability of longevity is only .2Telomeres are a type of DNA located at the ends of chromosomes. Each time the cell divides, it loses some of the telomere, until the cell no longer divides. Cells genetically engineered to replace telomere activity will have an extended lifespan.Free radicals are produced when oxygen breaks down molecules within a cell, stripping away an electron, creating a free radical. The free radical than looks for a replacement from somewhere else, and may destroy nearby cellular material, including DNA, proteins, and fats essential for cell functioning.Free radicals are thought to be involved in more than 60 disorders of aging, including heart disease, cancer, cataracts, and arthritis. Our bodies do produce some substances that neutralize them, but not enough to completely counteract effects.
4Aging 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 systemA decline in growth hormone is related to loss of muscle, increase of body fat and thinning of the skinDeclines in immune system functioningIncrease susceptibility to infectious and cardiovascular disease, and cancer.Fibers which are normally separate become cross linked, resulting in things like loss of flexibility in the skin and other organs, clouding of the lens of the eye, clogging of arteries, and kidney damage.RE: growth hormone, diet and exercise help control some of the negative effects due to loss of it. Replacing it in people with abnormally low levels has some negative effects.A COMBINATION OF THEORIES OF AGING PROBABLY BEST EXPLAINS THE PROCESS AT PRESENT.