The fact that it does mutate, slowly over time (generations) allows genetic genealogists to determine Genetic Distance between samples and also estimate change over the ages.
The International Society of Genetic Genealogists defines Genetic Distance as, “the term used to describe the number of differences or mutations between two sets of Y-chromosome DNA or mitochondrial DNA test results. A genetic distance of zero means that there are no differences in the two results and there is an exact match.”
Measuring a member’s Y-STR111 results against the PSHG Modal Haplotype provides clues for how DNA has mutated among the different member branches. This basic analysis depends on the property mentioned above, slowly occurring mutations. But what happens when DNA is changed by external forces like scientific advancements in gene replacement, or from prolonged time in outer space? What’s the effect on the results of autosomal or Y-DNA tests that we are familiar with today?
These articles don’t address the questions from a genetic genealogy perspective; but, I couldn’t help wonder – and think about the future.
Time’s The CRISPR Pioneers – http://time.com/time-person-of-the-year-2016-crispr-runner-up/
And, as reported from many news sources, long term space travel changes DNA – https://www.google.com/#q=dna+changes+in+space&safe=off&tbm=nws