Biology - Aging

Topics: Ageing, Senescence, Muscle Pages: 16 (5075 words) Published: April 29, 2013
Ageing can be defined as the progressive loss of functions that is accompanied by decreasing fertility and increasing age number. Ageing can be split up into two different categories; these are chronological aging and biological aging. Chronological aging is the measure of age in years and occurs at constant rate in all individuals. Biological aging is the progressive loss of function ability. For each individual, biological ageing depends on a combination of factors; some of these factors include genetic inheritance, finances and good health. Ageing occurs on all levels of bodily functions: cellular, organic and systemic. The process of aging cannot be stopped and represents the steady decrease in physiological ability to meet the demands that occur with increasing chronological age. During ageing the body goes through physical, structural and functional deterioration on the body. Physical changes include the whitening of the hair, wrinkling of the skin and the weakening of eyesight. The reason why human skin wrinkles is because of the fat layer under the skin thins and less collagen and elastin, which makes the skin tough and elastic, is produced as the body gets older. The reason as to why the body produces white hair is because hair follicles produce less pigment. Studies have even shown that the rate at which the human grows the fingernail declines gradually from the chronological age of 20 onwards. Structural changes include the weakening of the bones and joints. Lastly functional deterioration on the body is the weakening of organs and the different systems around the body. With all these deterioration going on in the body by biological and chronological ageing, it makes the body more vulnerable to more and more diseases. A possible link between aging and increased disease risk is the shortening or the dysfunction of telomeres. Telomeres are the lengths of repeating sequences of DNA found on the ends of chromosome. Telomeres are found the ends of DNA so that it can protect the ends of the chromosomes from damage during replication. However, the telomeres length shortens every time the chromosome replicates until cellular senescence occurs. This means that once telomeres get critically shot it leads to senescence where the cell is metabolically active but however unable to repair damages in the body or divide. When most of the chromosomes in the cell are senescent with the increasing of age, for example in tissue, the function of the tissue becomes damaged and shows an aged phenotype. Phenotype means the appearance of a particular trait, for example skin colour, according to the genetic makeup of the individuals DNA. Therefore, telomeres act as a serious mechanism for the age related decline in the body. If telomeres were not at the ends of chromosomes then chromosomes ends could fuse together and degrade the cell’s genetic information. This would make the cell malfunction, become cancerous or die. As broken DNA is dangerous, cells have the ability to sense and repair any chromosomes that are damaged. So without telomeres, all of the ends of chromosomes would look like broken DNA, meaning that the cells would try to fix the chromosomes that were not even broken. This process of fixing chromosomes that are not even broken would waste required energy that would be needed somewhere else, plus it would make the chromosomes to stop diving and eventually die. However, the lengths of telomeres vary from one species to another. The lengths of human telomeres are usually 5-12 kilobases. Kilobases are expressing the lengths of nucleic acid molecules. The lengths of mice and rats telomeres are much longer than humans and can be up to 150 kilobases based on their inbreeding status. This would be important to consider when understanding telomere data from animal studies. As mice and rats do not usually have long lifespan but have long telomeres this could mean that the telomere length is not critical to...
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