Explanation of SNPs with Extensions

SNPs which are found in more than one haplogroup used to be given names ending in a or b.More recent papers show these SNPs ending in .1 or .2. Earlier versions of the ISOGG tree show both names, but the current treeshows only the more recent notation.
Example:
      Current: 12f2.1    Former: 12f2a
      Current: 12f2.2    Former: 12f2b

SNPs that appear in a single haplogroup with multiple y-positions are now shown with extensions of _1, _2.
Example:
      P7_1, P7_2, P7_3.