Hayflick Limit

CORE DEFINITION

The Hayflick limit is the number of times a normal human cell population will divide before cell division stops. Empirical evidence shows that the telomeres attached to the DNA of each cell shorten slightly with each new cell division, until they reach a limit length. The concept of the Hayflick limit was proposed in 1961 by American anatomist Leonard Hayflick at the Wistar Institute in Philadelphia, Pennsylvania. Hayflick demonstrated that a normal human fetal cell population can divide 40-60 times in cell culture, after which the population enters senescence; this refuted the Nobel laureate Alexis Carrel's claim that normal cells are generally immortal. Each mitosis slightly shortens the telomeres attached to the DNA in cells, and the shortening of telomeres in the human body eventually leads to the inability of cells to divide; this mechanism of cellular senescence is related to the physiological aging of the whole body. This mechanism also appears to prevent genomic instability; the shortening of telomeres limits the number of cell divisions, thereby preventing the development of cancer cells in aging human cells.