{"id":2276,"date":"2026-07-02T13:53:21","date_gmt":"2026-07-02T13:53:21","guid":{"rendered":"https:\/\/one-peptides.com\/?p=2276"},"modified":"2026-09-27T19:18:00","modified_gmt":"2026-09-27T19:18:00","slug":"telomeres-and-ageing","status":"publish","type":"post","link":"https:\/\/one-peptides.com\/es\/telomeres-and-ageing\/","title":{"rendered":"Telomeres and ageing \u2014 telomere shortening and biological age in light of research"},"content":{"rendered":"

This article is educational in nature and constitutes a review of the published scientific literature on telomere biology and biomarkers of cellular ageing. It describes molecular mechanisms and the state of research, rather than use in humans. The text does not constitute medical or diagnostic advice. Some of the tools discussed (telomere length tests, epigenetic clocks) belong to the field of experimental research and diagnostics.<\/em><\/p>\n

Telomeres are repetitive stretches of DNA at the ends of chromosomes, protecting them from degradation and end-to-end fusion. With each division of a somatic cell the telomere shortens slightly \u2014 which is why its length is studied as one of the determinants of cellular ageing<\/a> and as a biomarker of biological age, alongside other molecular markers.<\/p>\n

What telomeres are \u2014 the ends of chromosomes<\/h2>\n

A linear chromosome has two ends, and each end is a problem. Without protection, the free end of a DNA strand looks to the cell like damage \u2014 the site of a break that the repair machinery attempts to “stitch” together. Were such stitching to occur, chromosomes would start to fuse end to end, leading to genetic chaos at division. The solution that evolution developed is the telomere.<\/p>\n

A telomere is a special structure at the end of a chromosome<\/strong>, built from a short DNA sequence repeated many times over. In humans and other vertebrates this is the sequence TTAGGG<\/strong>, repeated from hundreds to several thousand times at a single end. These repeats do not encode proteins \u2014 they serve a structural and protective function. Together with a set of associated proteins (a complex called shelterin), the telomere “caps” the end of the chromosome so that the cell does not read it as damage.<\/p>\n

An analogy that captures this role well is the plastic tip of a shoelace. As long as the tip is intact, the lace does not fray. A telomere works in a similar way \u2014 it protects the actual, coding part of the chromosome from “fraying” and from accidental fusion with another chromosome. As long as the telomere is sufficiently long, the cell treats the end of the chromosome as natural rather than as a defect to be repaired.<\/p>\n

Important for the topic of ageing is that telomere length is not constant. In most cells of the body it decreases over time \u2014 and it is precisely this change that has made telomeres the subject of intensive gerontological research.<\/p>\n

Why telomeres shorten \u2014 the end replication problem<\/h2>\n

Telomere shortening arises from a fundamental limitation in the way DNA is copied. It is known as the end replication problem<\/strong>.<\/p>\n

During each division, the cell must copy all of its genetic material. It does so using an enzyme \u2014 DNA polymerase. This enzyme, however, has a limitation: it can only extend a new strand in one direction and needs a short “starter” (primer) from which to begin. On one of the strands this leads to a situation in which the very end of the linear DNA molecule cannot be fully copied \u2014 once the last primer is removed, a small, unreplicated fragment remains. As a result, each successive copy of the chromosome is slightly shorter at the end than the previous one.<\/strong><\/p>\n

Were this loss to affect genes, it would be a catastrophe. Because, however, the ends carry telomeres \u2014 a buffer composed of non-coding TTAGGG repeats \u2014 it is these that absorb the loss. With each division the telomere loses some of its repeats, protecting the coding part of the chromosome. The telomere thus acts as an expendable buffer: it shortens so that the rest of the chromosome remains intact.<\/p>\n

This process, however, has its limit, first described even before the telomeres themselves were understood.<\/p>\n

The Hayflick limit.<\/strong> In the 1960s Leonard Hayflick observed that human somatic cells cultured in the laboratory do not divide indefinitely \u2014 after a certain, relatively constant number of divisions (on the order of a few dozen) they stop dividing. This boundary was named the Hayflick limit<\/strong>. For years it was unclear what determined it. Later work linked it precisely to telomere shortening: when a telomere shortens to a critical length, the cell registers this as an alarm signal.<\/p>\n

The effect of reaching this boundary is replicative senescence<\/strong> \u2014 a permanent arrest of division. A senescent cell usually does not die at once; it remains alive and metabolically active, but no longer divides. In the framework of ageing biology, critical telomere shortening is therefore sometimes described as one of the “counters” limiting the capacity of tissues to renew themselves. For this reason telomere length is sometimes compared to an internal division counter \u2014 with the caveat that this is a model, and the physiology of the whole organism is considerably more complex.<\/p>\n

It is worth noting that the rate of telomere shortening does not depend solely on the number of divisions. In studies, shortening is also influenced by oxidative stress and inflammation<\/strong> \u2014 factors that can accelerate the loss of telomere repeats independently of replication itself. This is one of the reasons why telomere length is studied in the context of lifestyle and chronic stress, and not merely as a simple division counter.<\/p>\n

Telomerase \u2014 the enzyme that lengthens telomeres<\/h2>\n

Since telomeres shorten with each division, a question arises: how does the organism maintain division-capable cells throughout life at all, and the species \u2014 across generations? The answer is an enzyme capable of rebuilding telomeres: telomerase<\/strong>.<\/p>\n

Telomerase is an enzyme that can add TTAGGG repeats<\/strong> to the end of a chromosome, counteracting their loss. It is a ribonucleoprotein \u2014 a complex of protein and an RNA molecule. The protein subunit (encoded by the TERT<\/strong> gene, telomerase reverse transcriptase) performs the catalytic function, while the built-in RNA molecule (the TERC component) serves as an internal template according to which the enzyme synthesises successive repeats. In this way telomerase solves the end replication problem \u2014 it adds what DNA polymerase cannot copy.<\/p>\n

Not all cells, however, have active telomerase. This distinction is at the heart of the entire topic:<\/p>\n