"Life clock" here refers to the "timer" that records everyone's life span, and is the "indicator" that life keeps moving towards the end. Does it really exist? Where is it? This problem has been puzzling people. According to years of research, scientists have finally found the "life clock". The official name of life clock is telomere.
Telomeres are the ends of chromosomes. Each chromosome has two ends, so there are two telomeres. Some people compare chromosome to shoelace, and telomere is the head of shoelace. Although the head of shoelace has the same composition as other parts of shoelace, the head of shoelace is stronger, which indicates that the structure of the head of shoelace is different from that of shoelace in some parts. In fact, the most important component of a chromosome is DNA, which is a double stranded molecule composed of deoxyribonucleotides carrying a, t, G and C bases according to the principle of A-T and G-C pairing. In addition to double strand, there is also single strand in telomere DNA structure. In addition, telomere DNA structure is basically composed of repeated units composed of TTAGGG. Telomere DNA contains 500-5000 such repeated units.
Scientists have found that telomere shortening is always accompanied by cell division in human body. In other words, telomere DNA always loses some base pairs every time a cell divides. Chinese scholar Tong tanjun and other researchers found that human fibroblasts in artificial culture, each division, telomere is a little short, in which about 49 base pairs of DNA are lost. If calculated according to the division limit determined by hehlick, the number of cell divisions in human body is 50, and the cell will lose 49 base pairs after one division. When telomere loses 49 × 50 = 2450 base pairs, fibroblasts will not divide and proliferate again. Failure to divide and proliferate means aging and death. It can be seen that the "life clock" in fibroblasts has 50 lattices, each of which is 49 base pairs apart. When the telomere loses 2450 base pairs, the "life clock" will become a "death knell".
As the normal activities of the human body need cell division and proliferation, once those division and proliferation cells in the human body ring the death knell, people's life will naturally reach the limit, then people will really die.