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Updated: Jun 10, 2026
12:08
Telomere Length and Telomerase Activity; A Yin and Yang of Cell Senescence
Published on: May 22, 2013
Telomere biology and immune system.
Karen S Hathcock1, Y Jeffrey Chiang, Richard J Hodes
1Experimental Immunology Branch, National Cancer Institute, 10 Center Drive, Bethesda, MD 20892, USA.
Discovery Medicine
|August 14, 2010
Summary
Cellular senescence, a state of limited cell division, is linked to telomere shortening. Telomeres protect chromosome ends, and their critical shortening triggers senescence or apoptosis.
Area of Science:
- Cell Biology
- Genetics
- Molecular Biology
Background:
- The Hayflick limit describes the finite replicative capacity of normal human somatic cells.
- Senescence, a state of irreversible cell cycle arrest, occurs after a limited number of cell divisions.
- Telomeres, DNA-protein structures at chromosome ends, are crucial for regulating cell proliferation.
Purpose of the Study:
- To explore the molecular mechanisms regulating somatic cell proliferation.
- To understand the role of telomeres in cellular senescence and apoptosis.
Main Methods:
- Review of existing research on cellular senescence and telomere biology.
- Analysis of the molecular composition and function of telomeres in mammalian cells.
Main Results:
- Telomeres, composed of (TTAGGG) repeats and associated proteins, protect chromosome ends.
- Progressive telomere shortening occurs with each cell division due to incomplete replication.
- Critically short telomeres lead to a loss of protective function, resulting in senescence or apoptosis.
Conclusions:
- Telomere length is a key regulator of somatic cell proliferation.
- Telomere shortening is a critical event triggering cellular senescence and apoptosis.
- Understanding telomere dynamics is essential for comprehending cellular aging and cancer biology.
Related Concept Videos
02:41Telomeres and Telomerase
In eukaryotic DNA replication, a single-stranded DNA fragment remains at the end of a chromosome after the removal of the final primer. This section of DNA cannot be replicated in the same manner as the rest of the strand because there is no 3’ end to which the newly synthesized DNA can attach. This non-replicated fragment results in gradual loss of the chromosomal DNA during each cell duplication. Additionally, it can induce a DNA damage response by enzymes that recognize single-stranded DNA.
02:41Telomeres and Telomerase
In eukaryotic DNA replication, a single-stranded DNA fragment remains at the end of a chromosome after the removal of the final primer. This section of DNA cannot be replicated in the same manner as the rest of the strand because there is no 3’ end to which the newly synthesized DNA can attach. This non-replicated fragment results in gradual loss of the chromosomal DNA during each cell duplication. Additionally, it can induce a DNA damage response by enzymes that recognize single-stranded DNA.
01:29Replication in Eukaryotes
In eukaryotic cells, DNA replication is highly conserved and tightly regulated. Multiple linear chromosomes must be duplicated with high fidelity before cell division, so there are many proteins that fulfill specialized roles in the replication process. Replication occurs in three phases: initiation, elongation, and termination, and ends with two complete sets of chromosomes in the nucleus.
Many Proteins Orchestrate Replication at the Origin
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02:31Replication in Eukaryotes
Overview
02:15Replicative Cell Senescence
Replicative cell senescence is a property of cells that allows them to divide a finite number of times throughout the organism's lifespan while preventing excessive proliferation. Replicative senescence is associated with the gradual loss of the telomere — short, repetitive DNA sequences found at the end of the chromosomes. Telomeres are bound by a group of proteins to form a protective cap on the ends of chromosomes. Embryonic stem cells express telomerase — an enzyme that adds the telomeric...
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