Telomere
Introduction
Telomeres are a region of repetitive nucleotide sequences at each end of a chromosome, which protect the end of the chromosome from deterioration or from fusion with neighboring chromosomes. Their discovery was a significant breakthrough in the field of genetics.
Structure and Function
Telomeres consist of repeated DNA sequences, primarily of the hexanucleotide TTAGGG in vertebrates, with the sequence varying in other organisms. They function by preventing the chromosome ends from being recognized as double-strand breaks (DSBs) and protecting them from end-to-end fusions and degradation.
Role in Cellular Aging
Telomeres play a crucial role in cellular aging. With each cell division, telomeres shorten. When they reach a critically short length, the cell enters a state of growth arrest known as senescence. This process is thought to prevent the propagation of cells with damaged DNA.
Telomerase Activity
Telomerase, an enzyme that adds DNA sequence repeats to the 3' end of DNA strands in the telomere regions, is active in some cells, which can prevent, slow, or even reverse the shortening of telomeres. This is particularly significant in stem cells and cancer cells.
Telomeres and Disease
Shortened telomeres are implicated in a wide range of diseases, including many forms of cancer, as well as aging-related diseases such as heart disease and dementia. Research is ongoing to understand the mechanisms behind these associations and to develop potential therapies.
Research and Future Directions
Research into telomeres and telomerase activity holds promise for the development of novel therapies for age-related diseases and cancer. Understanding the precise mechanisms by which telomere length influences disease risk and progression is a key area of focus.