Replicative fading was the degeneration of viable DNA that arose from the practice of reiterative cloning. Due to mutations in the DNA sequence, each successive clone had more deleterious conditions and genetic traits, a result of "genetic drift," since each generation was cloned from the generation before it. Eventually, this "fading" resulted in the complete inability for new viable clones to be created. The only solution to replicative fading that has been conclusively identified is to introduce DNA from non-cloned individuals, thus reducing the relative concentration of harmful mutations.

By 2365, the colony on the planet Mariposa was populated entirely by clones from five individuals and replicative fading was threatening their very existence. The colonists were encouraged to interbreed with a nearby colony even though they were socially incompatible. (TNG: "Up The Long Ladder")

It has been presumed, but never actually canonically stated, that deliberately favorably pre-mutating the donor DNA to be used for growing the reiterative clone will also minimize the possibility of replicative fading.
Presumably, that was how the original Dr. Stavos Keniclius was able to grow four successive generations of surrogates of himself, including Stavos Keniclius 5, in TAS: "The Infinite Vulcan" without a single one having undergone any replicative fading.
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