Replikatsioonilõplikud

Replikatsioonilõplikud refer to the terminal regions of DNA that are replicated during DNA replication. These regions pose a challenge for the cell's replication machinery, particularly in the case of linear chromosomes. Unlike the internal regions of DNA, which can be replicated continuously, the ends of linear chromosomes present a problem. This is because DNA polymerases, the enzymes responsible for DNA synthesis, require a primer to initiate replication. At the very end of a DNA strand, there is no upstream DNA to serve as a template for primer synthesis, leading to a potential shortening of the chromosome with each round of replication.

In eukaryotic organisms, this "end replication problem" is addressed by a specialized enzyme called telomerase. Telomerase is a ribonucleoprotein that extends the repetitive sequences found at the ends of chromosomes, known as telomeres. By adding these repetitive sequences, telomerase ensures that essential genetic information is not lost during replication. The presence and activity of telomerase are tightly regulated, and its role is crucial for maintaining genomic stability and preventing cellular senescence. In contrast, prokaryotic organisms typically have circular chromosomes, which do not have the same end replication problem as linear chromosomes.