In genetics, a founder mutation is a mutation that appears in the DNA of one or more individuals who are founders of a distinct population. Founder mutations initiate with changes that occur in the DNA and can get passed down to other generations.
Founder mutations originate in long stretches of DNA on a single chromosome—indeed, the original haplotype is the whole chromosome. As the generations progress, the proportion of the haplotype that is common to all carriers of the mutation is shortened (due to genetic recombination). This shortening allows scientists to roughly estimate the age of the mutation.