Telomere

Definition

A telomere is a repetitive nucleotide sequence located at the ends of linear chromosomes, which protects them from deterioration or fusion with neighboring chromosomes. These structures play a crucial role in maintaining genomic stability by preventing the loss of important DNA during cell division, and they are particularly significant in the context of how eukaryotic genomes are organized and maintained.

5 Must Know Facts For Your Next Test

1. Telomeres consist of repetitive sequences, typically composed of the nucleotides 'TTAGGG' in humans, and can vary among different species.
2. Every time a cell divides, its telomeres shorten due to the end-replication problem, leading to eventual cellular senescence when they become critically short.
3. Telomerase is an enzyme that can extend telomeres, allowing certain cells (like stem cells and cancer cells) to maintain their ability to divide indefinitely.
4. In eukaryotic organisms, telomeres serve as protective caps that prevent chromosomes from fusing together or being degraded during replication.
5. Telomere length is considered a marker of cellular aging; shorter telomeres are associated with age-related diseases and a decrease in overall cellular function.

Review Questions

• How do telomeres contribute to genomic stability during cell division?
  • Telomeres contribute to genomic stability by preventing the loss of essential DNA sequences at the ends of chromosomes during replication. When cells divide, the DNA replication machinery cannot completely replicate the very ends of linear chromosomes, leading to gradual telomere shortening. By protecting these ends from degradation and fusion with other chromosomes, telomeres ensure that vital genetic information remains intact throughout cell generations.
• Discuss the role of telomerase in cellular division and its implications for cancer development.
  • Telomerase is an enzyme that extends the length of telomeres, counteracting the natural shortening that occurs during cell division. In most somatic cells, telomerase activity is low or absent, leading to eventual senescence. However, in many cancer cells, telomerase is reactivated, allowing these cells to maintain their telomeres and proliferate uncontrollably. This ability to bypass normal cellular aging mechanisms is one of the hallmarks of cancer.
• Evaluate how telomere length might serve as a biomarker for aging and related diseases, considering both biological and environmental factors.
  • Telomere length serves as a potential biomarker for aging because it reflects cumulative cellular division and stress over time. Studies suggest that shorter telomeres are associated with age-related diseases such as cardiovascular disease and certain types of cancer. Various biological factors, such as genetic predisposition and hormonal influences, alongside environmental factors like stress, diet, and lifestyle choices, can impact telomere length. By evaluating these lengths in individuals, researchers can gain insights into their biological age and susceptibility to age-related health issues.

Related terms

Chromosome: A chromosome is a long, continuous thread of DNA that contains many genes and is coiled and condensed to fit within the cell nucleus.

Replication: Replication is the process by which a cell makes an exact copy of its DNA prior to cell division, ensuring that each daughter cell receives an identical set of chromosomes.

Senescence: Senescence refers to the process by which cells cease to divide and enter a state of permanent growth arrest, often linked to the shortening of telomeres.