Theories on the Causes of Genetic Disorders in the Elderly

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Genetic Conditions Leading to Mortality are Common in Older People than Younger People
Humans undergo several stages during their lifetime including growth, development, reproduction and senescence. Senescence is defined as the deteriorative biological changes that organisms experience as they age eventually leading to death. These changes include low metabolism, a weak immune system, memory loss, poor vision and loss of hearing. Senescence begins in humans during their post-reproductive years. However, gerontology research has shown that individuals who reproduce late have longer life spans compared to individuals who reproduce early. Nonetheless, it does not indicate that senescence is inevitable. All organisms experience senescence, but at different rates and time. Many genetic diseases such as Alzheimer’s disease and Huntington’s disease are prevalent in older individuals and the symptoms being to appear in middle adulthood. The causes of genetic diseases and disabilities in older individuals are explained by three evolutionary theories: antagonistic pleiotropy theory, mutation accumulation theory and disposable soma theory. These theories suggest that favorable natural selection and heavy allocation of resources for somatic maintenance during the reproductive period decreases the chances of genetic diseases in younger individuals.
The antagonist pleiotropy theory was introduced by Charles Williams in 1957. Pleiotropy occurs when one gene affects multiple traits in the body. The antagonistic pleiotropy theory asserts that natural selection favors genes that benefit fitness in early life despite their harmful effects in later life (Gavrilov and Gavrilova 341). Deleterious genes that occur in young adults are not passed onto...

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...nescence is result of a combination of the antagonist pleiotropy theory, mutation accumulation theory and disposable soma theory. The three evolutionary theories claim that natural selection is weak and ineffective in sustaining reproduction, growth, survival and somatic repair during the post-reproductive years causing genetic diseases in older individuals compared to younger individuals. As biological processes shut down, older individuals develop a weak immune system that can no longer fight the deleterious genes and mutations leading to death. Moreover, the evolutionary theories paved way for new research in gerontology that led to the development of new genetic theories of aging. The definite cause of genetic diseases in older individuals is yet to be determined, but all theories suggest that senescence is an inevitable process that all organisms experience.
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