aging.pdf

AGING GENOMICS C. R. Hemalatha  What is aging? Aging is a process that converts an optimally healthy, fit organism (for its environment) into a less healthy, less fit organism Aging is a biological process and not disease, per se Aging = reduced tissue/physiological fun...

AGING GENOMICS C. R. Hemalatha  What is aging? Aging is a process that converts an optimally healthy, fit organism (for its environment) into a less healthy, less fit organism Aging is a biological process and not disease, per se Aging = reduced tissue/physiological function Aging = increased susceptibility to disease (age- related diseases) Aging = decreased resistance to stress (physical & psychological)  Genetic Factors The aging process depends on a combination of both genetic and environmental factors Genetic factors seem more powerful than environmental factors in determining the large differences among people in aging & lifespan There are even some specific genetic disorders that speed up the aging process, such as – Hutchinson-Gilford – Werner’s and – Down syndromes  Environmental Factors Behaviours of a Healthy Lifestyle Not smoking Drinking alcohol in moderation Exercising Getting adequate rest Eating a diet high in fruits & vegetables Coping with stress Having a positive outlook Cellular Changes Associated - Aging  The rate at which cells multiply tends to slow down as we age  Certain cells that are important for our immune system to work properly (called T-cell lymphocytes) also decrease with age  Age also interferes with an important process called apoptosis, which programs cells to self-destruct or die at appropriate times  This process is necessary for tissues to remain healthy  It is important in slowing down immune responses once an infection has been cleared from the body  Cellular senescence Senescence is the state or process of ageing Cellular senescence - phenomenon where isolated cells demonstrate a limited ability to divide in culture This is known as Hayflick Limit, discovered by Leonard Hayflick in 1961 While organismal senescence is the ageing of organisms In humans & animals, cellular senescence attributed to the shortening of telomeres with each cell cycle; when telomeres become too short, the cells die  Organismal Senescence The length of telomeres is therefore the "molecular clock," predicted by Hayflick Telomere length is maintained in immortal cells (e.g. germ cells but not other skin cell types by the telomerase enzyme In the laboratory, mortal cell lines can be immortalized by the activation of their telomerase gene, present in all cells but active in few cell types  Cancer and Aging Cancerous cells must become immortal to multiply without limit Carcinogenesis implies, in 85% of cancers, the reactivation of their telomerase gene by mutation Since this mutation is rare, the telomere "clock" can be seen as a protective mechanism against cancer The clock must be located in the nucleus of each cell and the longevity clock Might be located in genes on either the 1st or 4th chromosome of the 23 pairs of human chromosomes Other genes are known to affect the ageing  Genes and Aging The sirtuin family of genes have been shown to have a significant effect on the lifespan of yeast & nematodes Over-expression of the RAS2 gene increases lifespan in yeast substantially Any doubts?