Search results
Results From The WOW.Com Content Network
The average cell will divide between 50 and 70 times before cell death. As the cell divides the telomeres on the end of the chromosome get smaller. The Hayflick limit is the theoretical limit to the number of times a cell may divide until the telomere becomes so short that division is inhibited and the cell enters senescence.
Measurements of telomere lengths across cell types at various ages suggest that this gradual chromosome shortening results in a gradual reduction in telomere length at a rate of approximately 25 nucleotides per year. [3]
Telomerase, also called terminal transferase, [1] is a ribonucleoprotein that adds a species-dependent telomere repeat sequence to the 3' end of telomeres. A telomere is a region of repetitive sequences at each end of the chromosomes of most eukaryotes. Telomeres protect the end of the chromosome from DNA damage or from fusion with neighbouring ...
The typical normal human fetal cell will divide between 50 and 70 times before experiencing senescence. As the cell divides, the telomeres on the ends of chromosomes shorten. The Hayflick limit is the limit on cell replication imposed by the shortening of telomeres with each division. This end stage is known as cellular senescence.
The successive shortening of the chromosomal telomeres with each cell cycle is also believed to limit the number of divisions of the cell, contributing to aging. After sufficient shortening, proteins responsible for maintaining telomere structure, such as TRF2, are displaced, resulting in the telomere being recognized as a site of a double ...
Senescence, an irreversible process in which the cell no longer divides, is a protective response to the shortening of the chromosome ends, called telomeres. The telomeres are long regions of repetitive noncoding DNA that cap chromosomes and undergo partial degradation each time a cell undergoes division (see Hayflick limit). [10]
Centromeres are the highly compact regions of chromosomes which join sister chromatids together and also allow the mitotic spindle to attach and separate sister chromatids during cell division. [17] Centromeres are composed of a 177 base pair tandem repeat named the α-satellite repeat. [ 16 ]
The temporal order of replication of all the segments in the genome, called its replication-timing program, can now be easily measured in two different ways. [1] One way simply measures the amount of the different DNA sequences along the length of the chromosome per cell.