On monday, we will discuss the following hypotheses of aging:

Antagonistic Pleiotropy is the concept that a gene for survival or a gene that promotes
reproduction early can be selected for even if it kills you at a later
age. So selection favors juvenile survival at the expense of old age survival. This hypothesis recognizes that most traits have both costs and benefits, and are tradeoffs. The tradeoff in antagonistic pleiotropy is improved health in youth, but disease in old age.

Declining power of selection hypothesis of aging: Genes for maintenance and repair of the body are selected for more strongly at early ages (pre-reproduction) than after reproductive
age. For this: imagine a gene mutation that prevents cancer at age 10 and another gene mutation that prevents cancer at age 100. The gene that prevents cancer at age 100 will not have any effect most of the time because most people are dead by age 100 (this remains true even if you take senescence out of the equation – random accidents will claim many lives). The gene that affects 10 year olds is more likely to be expressed and have a benefit simply because most people are alive at age 10. Therefore the old-age gene will be invisible to natural selection, the 10 year old gene will be subject to positive selection.

Disposable Soma hypothesis; This hypothesis recognizes that the nonreproductive part of the body (the soma) exists only to support the reproductive part of the body. At any moment in time an adult can devote energy to the maintenance of the body or to reproduction. Put simply, after successful reproduction, the soma is “disposable”, and genes are passed on. This tradeoff is vividly illustrated in adult salmon, which appear to do all their aging at once, immediately after a single reproductive effort. In many animals, bearing offspring shortens lifespan. There is some evidence of this in humans too.

Optional readings for the weekend:

age-old-question

understanding-aging

There is no writing project due.Keep working on your final projects. Congratulations to those who have already presented their topics. Excellent work so far!! And good luck to those getting ready to present this upcoming week.

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Update!

Here is the handout of slides for mondays lecture:aging

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Joe Alcock

Emergency Physician, Educator, Researcher, interested in the microbiome, evolution, and medicine