What is the role of telomeres in DNA replication?

Telomeres play a crucial role in DNA replication by protecting the ends of chromosomes from degradation and fusion.

Telomeres are repetitive sequences of non-coding DNA that cap the ends of chromosomes, acting like the plastic tips on shoelaces that prevent them from fraying. They are essential for maintaining the integrity of our genetic information during DNA replication. Every time a cell divides, the DNA within it must be replicated so that each new cell receives a complete set of chromosomes. However, due to the limitations of the DNA replication machinery, the very ends of the chromosomes cannot be fully replicated. This results in the loss of some genetic material during each round of cell division.

To counteract this, telomeres act as a buffer zone, taking the hit for this loss. They shorten with each cell division, protecting the vital genetic information in the rest of the chromosome. When telomeres become critically short, the cell can no longer divide and becomes senescent or dies. This is a key aspect of ageing at the cellular level.

Telomeres also play a role in preventing the fusion of chromosomes. Without telomeres, the sticky ends of linear DNA molecules would be exposed and could accidentally join together. This could lead to serious genetic abnormalities and diseases, including cancer. Telomeres prevent this by providing a physical barrier that keeps chromosome ends apart.

Furthermore, telomeres are associated with a protein complex called shelterin, which helps to protect the chromosome ends and regulate telomere length. This complex also plays a role in preventing the DNA damage response system from recognising and acting upon the chromosome ends as if they were broken DNA strands.

In summary, telomeres are vital for preserving the genetic information during DNA replication, preventing chromosome fusion, and regulating cell lifespan. They are a key component of our cells' anti-ageing and anti-cancer defence mechanisms.