What are telomeres?
Telomeres are structures located at the ends of chromosomes that protect genetic material during cell division. Telomeres prevent chromosomes from binding with other chromosomes, fusing with themselves, and "fraying".
Based on their general function and appearance, telomeres are often compared to the plastic caps on shoelaces. As they are also associated with disease and eventual death, telomeres have also been compared to a bomb fuse.
The human body is composed of trillions of cells. Over time, cells endure "wear and tear" and eventually need to regenerate. Once a cell "wears out" it replicates itself and divides, creating a brand new cell. Many cells will divide 40-60 times during the course of a human lifetime. The number of times a cell divides before it dies is known as the Hayflick limit, named after Leonard Hayflick, an American scientist who discovered this limitation in 1961-62.
In most cases, each time a cell divides it sheds a portion of its telomeres. As the cell continues to divide its telomeres get shorter and shorter. Once the telomeres are gone the chromosome has no buffer to protect its genetic material during cell division. As a result, the cell can no longer divide and dies. The process a cell undergoes after maturity is known as cellular senescence.