The Dividing of Cells Leading to Our Death

URL: http://www.youtube.com/watch?v=jqCo-McgHLw
Date of Publication: October 21, 2012
Youtube Username: scischow

Summary:
Hank talks about death with aging and how no one actually dies of just old age, death always has a reason. Some animals can live for a very long time and Hank tells us why we age and might we extend that process not just by exercise or eating healthy. A process which humans and animals go through is called senescence happens after humans reach sexual maturity and after that we lose able to combat disease and many other things. However some animals exhibit negligible senescence where they dont lose ability to reproduce with time and basically stay at same level of fitness until their death which might be disease or an accident. The reason why some animals/humans start to die as soon as they reproduce is because our cells have their own deaths programed into them. Our cells are constantly dividing and making copies of themselves and a scientist Leonard Hayflick discovered that human cells just stop dividing and die after a certain limit. The Hayflick Limit is the number of times a cell can divide and this number can be less or more for some animals. So, as humans live on and their cells divide, we reach closer to that limit and that is when we die. Then Hank goes on to describe why there is a limit in the first place and it is because of its chromosomes and the cell quits dividing after not being able to completely copy its telomeres which are DNA at the ends of the chromosome. Each time it is copied the telomere gets a bit shorter than the parent and it reaches the limit to not be able to replicate again when the telomere gets too short to copy. This is why we have the Hayflick Limit. The reason why we dont just add telomeres to us to be able to have our cells to keep on dividing forever is because of the risk of cancer. Cancer cells can sometimes create their own telomerase causing them to divide like crazy without their chromosomes getting damaged which results in tumors. Hank continues to talk about how our genes and calories are also part of the process of aging. A gene call DAF-2 discovered in a worm was the only reason why the worm was aging and if frozen it made the worm live twice as long. Also a gene called DAF-16 that keeps the worm up and going and "spunky" and when the DAF-2 gene is damaged the DAF-16 gene takes over. However, this is not yet tested on people because something that works on mice may not work on people. Calorie intake stimulate IGF-1 which is a growth hormone, basically calorie intake stimulates the aging process. Also IGF-1's main job to direct food energy towards growth and fewer calorie intake shifts your metabolism gears to maintaing existing cells instead of growing which means a high resistance of stress and disease. However, people should not go on an insane diet because things that work on mice may not necessarily work on people.


Relevance:
 This video talks about the aging process and why we age. The Hayflick Limit being the number of times a cell can divide and once it reaches that limit the cell dies, which is one of the main reasons we age. The video also explains why we have this limit in the first place. This is related because we are currently learning about mitosis and how that cell actually does its dividing. We are also learning about how cancer cells divide out of control and the video also talks about how because of why the Hayflick Limit exists is also how some cancer cells divide like crazy and form tumors.