What type of plant did Gregor Johann Mendel use to discover the effects of genetics on characteristics?

Gregor Johann Mendel used the garden pea plant (Pisum sativum) to conduct his experiments on inheritance. The pea plant was an ideal choice for Mendel because it had several distinct traits that could be easily observed, such as flower color, seed shape, and pod color. Additionally, pea plants can self-fertilize as well as cross-fertilize, which allowed Mendel to control the breeding and observe how certain traits were passed on from one generation to the next.

Mendel's experiments established the foundational principles of genetics, including the concepts of dominant and recessive traits, and the segregation and independent assortment of alleles. His meticulous approach and the clarity of the pea plant's characteristics led to the formulation of Mendel's laws of inheritance, which are still relevant in the study of genetics today.

While corn, beans, and barley are all important crops in agriculture and genetics has been studied in these species, Mendel's specific contributions and discoveries stemmed from his work with the pea plant. Therefore, the garden pea is the correct answer as it was central to Mendel's groundbreaking research in the field of genetics.