One hundred and fifty years ago, Gregor Mendel investigated the segregation of seven traits in pea (Pisum sativum) and established the law of segregation and the law of independent assortment in genetics. After the two laws of genetics were rediscovered in 1900, the seven traits have been extensively investigated in the fields of plant physiology and biochemistry as well as in the cell and molecular levels. Recently, with the development of molecular technology in genetics, four genes for seed shape (R), stem length (Le), cotyledon colour (I), and flower colour (A) have been cloned and sequenced; and another three genes for immature pod colour (Gp), fasciation (Fa) and pod form (V) have been located in the linkage groups, respectively. The identification and cloning of the four Mendel's genes will help deeply understand the basic concept of gene in many respects: like the diversity of gene function, the different origins for gene mutation in molecular level, and the molecular nature of a dominant gene or a recessive gene. In teaching of genetics, the introduction of most recent research advancements of cloning of Mendel's genes to the students and the interpretation of the Mendel's laws in molecular level will help students promote their learning interests in genetics and help students grasp the whole content from classical genetics to molecular genetics and the developmental direction of this subject.