Measuring Telomere Length: A Timeline Review on the State-of-Art Techniques

Telomeres are highly specialized structures capping the end of each chromosome; they guarantee the integrity of the genome during replication process. Composed of repetitive sequences, especially of the type 5’TTAGGG-3′, they vary from 5 kb to 15 kb in length in humans, and are dependent on telomerase, a reverse transcriptase enzyme to maintain their integrity. In most cases, shortening of telomeres leads to genomic instability, consequently triggering cell death mechanisms, while elongation is associated with cell immortalization. Consequently, telomere length has become a promising biomarker for several pathologies. Telomere measurement techniques evolved during time, and are based on Southern blotting, molecular cytogenetic and quantitative polymerase chain reaction approaches, and most recently, on bioinformatics evaluating next generation sequencing data. Here, these techniques are reviewed with their variations for measuring telomere lengths together with their main applications.