There are two meanings for Genetic Distance:

  1. Genetic Distance is the number of differences, or mutations, between two
    sets of results. A genetic distance of zero means there are no differences in
    the results being compared against one another, i.e., an exact match. This is
    the meaning when comparing Y-chromosome DNA or mitochondrial DNA.
  2. For autosomal DNA comparisons, genetic distance may refer to the size of a
    DNA segment. The genetic distance is then the length of the segment in
    centiMorgans.