- The GM diff (green) treats homozygous differences (AA vs aa) the same as an allele difference (AA vs Aa) or (aa vs Aa). The AM diff (orange) is sensitive to allele differences between homozygotes (AA or aa) and heterozygotes (Aa). The TiTv diff (blue) is sensitive to allele differences but further distinguishes between transition and transversion allele changes, treating transition genotypes as more similar than the corresponding transversion genotypes