The discovery credited to Gregor Mendel in the study of genetics is the fundamental principles of inheritance. Mendel's experiments with pea plants led to the formulation of the laws of segregation and independent assortment. Through careful observation and statistical analysis, he identified how traits are passed from parents to offspring and how dominant and recessive alleles interact. Mendel's work laid the foundation for modern genetics, influencing our understanding of heredity, genetic variation, and the predictability of trait inheritance across generations.