Who discovered the predictable patterns of inheritable traits?
Gregor Johann Mendel: see The Mendelevian Genetics of Inheritance.
The theory states that there is inheritable variation among offspring, and that as environments change some variations will enjoy an advantage over others. In other words, there will be preferential survival of beneficial inheritable traits, which will ultimately be reflected in the general population. This constitutes evolution.
If Gregor Mendel didn't use plants that were not true breeding then would he have discovered dominant and recessive traits?
Heredity is the passing of traits and features from the parents to the offspring. Hereditary traits can include growth patterns, which can differ from the growth patterns of another race. For example, many Japanese people are shorter than a lot of European people, and Dutch people are considered very tall compared to other Europeans.