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Definition: How do telomeres protect the integrity of DNA?

Telomeres are repetitive DNA sequences located at the ends of chromosomes. They play a crucial role in protecting the integrity of DNA during cell division and preventing the loss of genetic information.

Telomere Structure

Telomeres consist of short tandem repeats of nucleotide sequences, typically composed of the sequence “TTAGGG” in humans. These repetitive sequences do not code for any specific protein or genetic information. Telomeres also contain associated proteins that help maintain their structure and function.

Telomere Function

During DNA replication, the enzyme responsible for copying DNA, called DNA polymerase, cannot fully replicate the ends of linear chromosomes. This is due to the “end replication problem” where the last few nucleotides at the 3′ end of the template strand cannot be copied. As a result, with each round of DNA replication, the telomeres progressively shorten.

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Protective Role of Telomeres

Telomeres act as protective caps at the ends of chromosomes, preventing the loss of genetic material. Their repetitive nature allows them to be shortened without affecting the essential genetic information encoded in the rest of the chromosome.

Additionally, telomeres help prevent the fusion of chromosome ends, which could lead to genomic instability and DNA damage. They achieve this by forming a protective loop structure called a T-loop, where the single-stranded telomeric DNA invades and pairs with a complementary region within the double-stranded telomeric DNA.

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Telomere Length and Cellular Aging

As telomeres shorten with each cell division, they eventually reach a critical length. At this point, the cell’s ability to divide is compromised, leading to cellular senescence or programmed cell death (apoptosis). This process is believed to contribute to the aging of tissues and organs.

Telomere length is regulated by the enzyme telomerase, which can add telomeric DNA sequences to the ends of chromosomes, counteracting the shortening process. Telomerase is highly active in embryonic cells, stem cells, and certain types of cancer cells, allowing them to maintain longer telomeres and continue dividing indefinitely.

In summary, telomeres play a vital role in protecting the integrity of DNA by preventing the loss of genetic information and maintaining chromosome stability. Understanding telomere biology and its relationship to cellular aging has important implications for longevity research and potential interventions to promote healthy aging.

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Keywords: telomeres, genetic, telomere, sequences, chromosomes, information, integrity, repetitive, preventing