The study noted here provides numbers for the mutation rates in muscle stem cells, the stochastic damage that occurs over time as small numbers of errors slip past the highly efficient molecular machinery of cellular replication and DNA repair. The researchers used single cell genomic sequencing, a very useful and still comparatively new capability. It produces a much more detailed view of the state of nuclear DNA inside a cell population, showing the enormous variations in stochastic mutational damage that takes place over the years. Every cell has thousands of different areas of damage in their DNA, and it is becoming apparent that the damage in stem cell populations is cloned out into tissues. Stem cells maintain tissues by providing a supply of somatic cells, and those somatic cells divide many times before they reach the Hayflick limit. So the mutations present in a stem cell will over time propagate into a fraction of the supported tissue.
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