TTAGGG

Definition

TTAGGG is a repetitive DNA sequence known as a telomere repeat, which is found at the ends of linear chromosomes in eukaryotic cells. This sequence plays a crucial role in protecting chromosomes from degradation and preventing the loss of important genetic information during DNA replication. Telomeres, consisting of many TTAGGG repeats, shorten with each cell division, which is associated with aging and cellular senescence.

5 Must Know Facts For Your Next Test

1. The TTAGGG sequence is repeated thousands of times in human telomeres, forming a protective buffer zone that prevents loss of coding DNA during cell division.
2. As cells divide, the telomeres shorten due to the end-replication problem, which can lead to eventual cell death when they become too short.
3. Telomerase is highly active in germ cells and stem cells, allowing these cells to maintain their telomere length and continue dividing indefinitely.
4. In somatic cells, telomerase activity is usually low or absent, contributing to the aging process and limiting the number of times a cell can divide.
5. Abnormal telomere length has been linked to various diseases, including cancer, where cancer cells often reactivate telomerase to maintain their proliferative capabilities.

Review Questions

• How does the TTAGGG sequence contribute to chromosome stability during DNA replication?
  • The TTAGGG sequence serves as a protective telomere repeat that safeguards the ends of chromosomes from degradation during DNA replication. When DNA is copied, the enzymes involved cannot fully replicate the very end of linear chromosomes, leading to potential loss of genetic information. The presence of telomeres with repeating TTAGGG sequences helps ensure that essential coding regions are not lost, maintaining chromosome integrity through multiple rounds of cell division.
• Discuss the role of telomerase in maintaining telomere length and how it relates to cellular aging.
  • Telomerase is an enzyme that adds TTAGGG repeats back onto the ends of chromosomes, counteracting the natural shortening that occurs during DNA replication. This activity is particularly prominent in germ cells and stem cells, allowing them to sustain their ability to divide. In contrast, most somatic cells exhibit low or absent telomerase activity, leading to progressive telomere shortening with each division, which ultimately contributes to cellular aging and limits the replicative potential of these cells.
• Evaluate the implications of telomere shortening and telomerase reactivation in cancer development.
  • Telomere shortening acts as a biological clock for normal somatic cells, limiting their ability to divide and preventing uncontrolled growth. However, many cancer cells bypass this limit by reactivating telomerase, enabling them to maintain or even lengthen their telomeres. This reactivation allows cancer cells to proliferate indefinitely, contributing to tumorigenesis. Understanding the mechanisms behind telomere dynamics provides insights into potential therapeutic strategies targeting telomerase in cancer treatment.

Related terms

Telomeres: The protective caps located at the ends of linear chromosomes, made up of repetitive nucleotide sequences like TTAGGG.

Telomerase: An enzyme that adds telomere repeats to the ends of chromosomes, helping to maintain telomere length and counteract the shortening that occurs during DNA replication.

Chromosome: A long DNA molecule containing genetic material, which is organized into genes and located in the nucleus of eukaryotic cells.