Telomere

Definition

A telomere is a repetitive nucleotide sequence at the ends of linear chromosomes that protects them from deterioration or fusion with neighboring chromosomes. These structures play a crucial role in maintaining chromosome stability and integrity, ensuring that genetic information is accurately passed on during cell division. Over time, telomeres shorten with each cell division, which is linked to aging and cellular senescence.

5 Must Know Facts For Your Next Test

1. Telomeres consist of repetitive sequences, typically composed of the sequence 'TTAGGG' in humans, which can extend for thousands of bases.
2. Each time a cell divides, the telomeres become shorter because DNA polymerase cannot fully replicate the ends of linear chromosomes.
3. Once telomeres reach a critical length, the cell can no longer divide and enters a state known as senescence, contributing to the aging process.
4. Certain types of cells, such as stem cells and germ cells, have higher levels of telomerase, which helps maintain telomere length and allows for continued cell division.
5. In cancer cells, telomerase is often reactivated, allowing these cells to avoid normal senescence and continue dividing uncontrollably.

Review Questions

• How do telomeres contribute to chromosome stability during cell division?
  • Telomeres act as protective caps at the ends of chromosomes, preventing them from fraying or sticking to each other during cell division. This protection is crucial because it ensures that the genetic information within the chromosomes remains intact and is accurately passed on to daughter cells. Without functioning telomeres, chromosomes could lose important genetic material or undergo rearrangements, leading to potential genomic instability.
• What role does telomerase play in specific types of cells, and how does this relate to cancer biology?
  • Telomerase is an enzyme that extends the telomeres by adding nucleotide sequences back to their ends. This activity is particularly important in stem cells and germ cells, where it allows these cells to maintain their ability to divide indefinitely. In cancer biology, many tumor cells reactivate telomerase, which enables them to bypass normal cellular senescence. This reactivation contributes to the uncontrolled proliferation characteristic of cancerous growths.
• Evaluate the implications of telomere shortening on aging and potential therapeutic approaches targeting telomerase in regenerative medicine.
  • Telomere shortening has significant implications for aging, as it limits the number of times a cell can divide before entering senescence. This process contributes to age-related diseases and decreased tissue regeneration. Therapeutic approaches targeting telomerase aim to counteract this shortening by enhancing telomerase activity in somatic cells or using it in regenerative medicine. However, such strategies must be approached with caution since excessive telomerase activity can lead to uncontrolled cell growth and cancer development.

Related terms

Chromosome: A structure made of DNA and protein that carries genetic information and is found in the nucleus of eukaryotic cells.

Telomerase: An enzyme that adds nucleotide sequences to the ends of telomeres, helping to maintain their length and function, particularly in stem cells and cancer cells.

Senescence: The process by which cells cease to divide and enter a state of permanent growth arrest, often associated with aging and telomere shortening.