Sunday, April 6, 2014
Why Do We Age?
When I was in high school I learned that every man would eventually develop prostate cancer if he lived long enough, because it is inevitable with age. I was, in a way, relieved. Immortality terrified me more than certain death. I understand that we age, but I still have trouble not attributing it to "wear and tear" the beginning of the Why Do We Age? article falsifies. After reproduction, we have succeeded in doing what we were made to do - produce fit offspring - and thus, it makes sense for our bodies to deteriorate as they are no longer needed. Regardless, I found the article to provide in interesting insight into senescence. As for increased chances of acquiring a malignant tumor or growth, maybe the pleiotropic theory is accurate. Perhaps there is a mechanism, in the endocrine or reproductive systems, which is beneficial for reproduction but deleterious later in life. What I found most interesting in the article was life-history plasticity. In the experiment with nematodes, I expected them to age more rapidly under such intense caloric restriction. However, when I more closely examine the situation, they needed to reproduce before they aged too much. This article made me think more than some others we have read, about age, death, and number of offspring. I think when examining senescence it is most imperative to take reproduction into account, as that is our primary purpose, as animals. While genetics, environment, personal fitness and lifestyle certainly play a role in aging, I think of aging as less of a purpose-fulfilling stage and more of an after-effect to a (hopefully) wonderful life.
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Before reading the paper “Why Do We Age?” I also thought that aging was caused by “wear and tear” by a process that was unrelated to genes and their expression. After reading the paper however, while I now know how much of a role genetics can play in ageing, I still believe that the “wear and tear” contributes a significant amount to the explanation of aging. By this I mean that while certain genes can increase the longevity and youthfulness of someone’s life, they will not completely protect someone from senescence. My thought process behind this belief is due to the “imperfectness” or the mistakes that occur during replication of the genome as well as growth and repair of cells. This is the same “imperfectness” responsible for the mutations (mistakes in the genome) that contribute to the variation within organisms. The longer a person lives, the higher the number of mistakes that occur in the genome (due to environmental factors or just mistakes in DNA replication). Although repair mechanisms in the cell may sometimes catch these errors, sometimes they might skip over them as a “mistake” or if the damage too much to be repaired. Whatever the case, the person in context will begin to accumulate errors in their genome that may detrimental in maintaining their “youthfulness” and promote the process of aging.
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ReplyDeleteSince we're on the topic of genetics, I'd also like to mention that telomeres (something we heard about in the stress unit) have also shown to play a role in the process of aging. Studies show that older individuals tend to have shorter telomeres on their chromosomes. Each time we replicate our cells, the ends of the DNA slowly get shorter which accumulates over a lifetime until they reach a critical point where the actual genes become endangered. On the other hand, if our telomeres did not shorten, we would have “immortal cells” and would be at a much higher risk of cancer. Cell senescence might be an adaptation to prevent cancer, but the tradeoff is that eventually we will die. If we saw a balance between these two, we might see an increase in longevity.
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