Law of Unit Characters
Breeding and testing about 5,000 pea plants, he was able to come up with crucial generalizations that were later on used as founding principles of the Mendelian inheritance or Mendel's Principles of Heredity. The so-called "Mendel's laws of inheritance" came about based on the set of principles of Gregor Mendel. These laws are the Law of Segregation, the Law of Independent Assortment, the Law of Dominance, and the Law of Unit Characters.
Gregor Mendel set seminal theories on heredity and variation. In Law of Unit Characters, he described the unit characters as the factors of inheritance. These factors are now referred to as genes. These unit factors, accordingly, are the ones responsible for the variations in inherited characteristics.
He further argued that these unit factors (genes) exist in two sets or in pairs where one set is inherited from each parent. Thus, for every biological trait, there are two unit factors in pairs that control the same trait. This pair is now called alleles. For instance, a pair of alleles controlling a particular trait, i.e. eye color, one allele would code for blue eyes and another allele, for brown eyes.