A brief intro to telomeres — explained with excellent art.
Telomeres play an important role in the human body, specifically in our cells. Before we can further study them, it’s great to get a quick understanding of what they are.
Located in the nucleus of a cell in your body are chromosomes, pictured below. They’re typically expressed as an X shape, and each side is called a sister chromatid.
Now, if we were to zoom in closely enough, we’d be able to see that there are protective caps at the ends of each chromosome. This is called a telomere. Telomeres contain repeated DNA sequences of TTAGGG.
What’s its function? Telomeres keep the ends of a chromosome from fraying or sticking together abnormally. A common analogy, in this case, is the hard part at the end of a shoelace. The aglet keeps the shoelace threads from unwinding.
Depending on the type of tissue and replicating history of the cells, most chromosomes have around 0.5 to 15 kilobase (kb) pairs of telomere repeats. Different chromosome ends have different telomere lengths (i.e. chromosome 17 tends to have shorter telomeres than most of the others).
Unfortunately, each time a cell undergoes cell division, the telomeres get shorter. They’re constantly worn down until eventually, the cell can no longer divide (since the telomeres are too short). That’s when the cell reaches the Hayflick Limit — named after Leonard Hayflick, who proposed that human cells have a limited number of cell divisions (40 to 60, to be exact).
Once the cell stops dividing, it undergoes apoptosis — or programmed cell death.
Scientists have been researching ways to lengthen telomeres using an enzyme called telomerase, which activates genes to extend the telomeres in our bodies. We hope that in the future, we will be able to solve many issues regarding mutations — and even aging — with telomeres.
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Go deeper into telomeres through these articles.
Telomeres and Aging
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