The Hayflick limit is the number of times a cell can divide. Any normal, human cell cannot live indefinitely, it will die eventually however it multiplies many times before that death happens. A cell divides thorough the process of mitosis which starts with interphase (G1, S, G2 phases) and then going through Prophase, Metaphase, Anaphase, and Telophase. This results in cytokinesis where two identical daughter cells is the result. During interphase, many important things occur to the cell such as DNA replication and doubling its organelles. Once that finished, Prophase, Metaphase, Anaphase, and Telophase occurs with the cell. During these steps, the chromosomes in the cell are lined up in the middle and then attached to spindle fibers who pull them apart. The cell then pinches itself with half of the chromatids on one side and the other half on the other side, thus created two twin-like daughter cells. Leonard Hayflick published a paper in 1961 that explained normal cells reach their limit when they've doubled about fifty times. This piece of work become cited all over the world, “it was an epiphany” (Skloot, 2010, p. 217). Scientists were trying to grow immortal cells using normal cells, but that was not possible according to Hayflick’s limit. Cells were bound to die because they cannot divide forever. Scientists didn't understand that only special cells such as cells that were transformed “by a virus or a genetic mutation had the potential to become immortal” (Skloot, 2010, p. 217).
Going even deeper into what Nishrat said, the Hayflick limit is indeed the amount of times a cell can multiply before it dies, specifically the time it takes for the telomere to run out. After studied cellular replication, scientists fond out that the cause of what is now called the Hayflick Limit is that "the string of DNA at the end of each chromosome called a telomere...[shortens] a tiny bit each time a cell [divides]" (Skloot 217). The length of the telomere is directly proportional to the age of the specimen. Every time the DNA replicates and the cell divides, the telomere shortens until there is no more, causing the cell to die. Basically, the telomere to the cell is like a wick to a candle; they keep the "fire" going on and the time remaining is equivalent to the length remaining.
In addition to this, the Hayflick Limit explains the mechanism of cellular aging. The concept says that normal human cells can only replicate and divide forty to sixty times before they can’t divide anymore and will break down by apoptosis. The Hayflick Limit helped scientists study the cellular aging on human populations from embryonic development to death, also the effects of shortening repetitive sequences of DNA, called telomeres. Dr. Hayflick had notices that the cells that were grown in cultures reproduced by dividing. They produce facsimiles an finite number of times before the process stops and the cell ends up dying. Hayflick also found out that a cell goes three phases: cell division which is the rapid phase, mitosis goes slow and senescence when the cell stops dividing completely. “Scientists knew from studying HeLa that cancer cells could divide indefinitely, and they’d speculated for years about whether cancer was caused by an error in the mechanism that made cells die when they reached the Hayflick Limit. They also knew that there was a string of DNA at the end of each chromosome called a telomere, which shortened a tiny bit each time a cell divided, like time ticking off a clock” (Skloot 217). Clark, J. (n.d.). Will the Hayflick limit keep us from living forever? Retrieved January 18, 2015, from http://science.howstuffworks.com/life/genetic/hayflick-limit.htm
The Hayflick limit is the number of times a cell can divide. Any normal, human cell cannot live indefinitely, it will die eventually however it multiplies many times before that death happens. A cell divides thorough the process of mitosis which starts with interphase (G1, S, G2 phases) and then going through Prophase, Metaphase, Anaphase, and Telophase. This results in cytokinesis where two identical daughter cells is the result. During interphase, many important things occur to the cell such as DNA replication and doubling its organelles. Once that finished, Prophase, Metaphase, Anaphase, and Telophase occurs with the cell. During these steps, the chromosomes in the cell are lined up in the middle and then attached to spindle fibers who pull them apart. The cell then pinches itself with half of the chromatids on one side and the other half on the other side, thus created two twin-like daughter cells. Leonard Hayflick published a paper in 1961 that explained normal cells reach their limit when they've doubled about fifty times. This piece of work become cited all over the world, “it was an epiphany” (Skloot, 2010, p. 217). Scientists were trying to grow immortal cells using normal cells, but that was not possible according to Hayflick’s limit. Cells were bound to die because they cannot divide forever. Scientists didn't understand that only special cells such as cells that were transformed “by a virus or a genetic mutation had the potential to become immortal” (Skloot, 2010, p. 217).
ReplyDeleteGoing even deeper into what Nishrat said, the Hayflick limit is indeed the amount of times a cell can multiply before it dies, specifically the time it takes for the telomere to run out. After studied cellular replication, scientists fond out that the cause of what is now called the Hayflick Limit is that "the string of DNA at the end of each chromosome called a telomere...[shortens] a tiny bit each time a cell [divides]" (Skloot 217). The length of the telomere is directly proportional to the age of the specimen. Every time the DNA replicates and the cell divides, the telomere shortens until there is no more, causing the cell to die. Basically, the telomere to the cell is like a wick to a candle; they keep the "fire" going on and the time remaining is equivalent to the length remaining.
DeleteIn addition to this, the Hayflick Limit explains the mechanism of cellular aging. The concept says that normal human cells can only replicate and divide forty to sixty times before they can’t divide anymore and will break down by apoptosis. The Hayflick Limit helped scientists study the cellular aging on human populations from embryonic development to death, also the effects of shortening repetitive sequences of DNA, called telomeres. Dr. Hayflick had notices that the cells that were grown in cultures reproduced by dividing. They produce facsimiles an finite number of times before the process stops and the cell ends up dying. Hayflick also found out that a cell goes three phases: cell division which is the rapid phase, mitosis goes slow and senescence when the cell stops dividing completely. “Scientists knew from studying HeLa that cancer cells could divide indefinitely, and they’d speculated for years about whether cancer was caused by an error in the mechanism that made cells die when they reached the Hayflick Limit. They also knew that there was a string of DNA at the end of each chromosome called a telomere, which shortened a tiny bit each time a cell divided, like time ticking off a clock” (Skloot 217).
DeleteClark, J. (n.d.). Will the Hayflick limit keep us from living forever? Retrieved January 18, 2015, from http://science.howstuffworks.com/life/genetic/hayflick-limit.htm