In many cases the Mendelian 3 : 1 and 9 : 3 : 3 : 1 ratios are not found in genetic tests. This is called non-Mendelian inheritance or Beding inheritance. Due to non-Mendelian inheritance, the ratio of 1 : 2 : 1, 2 : 1, 9 : 7, 13 : 3 etc. is found in genetic tests.