Gregor Mendel was an Austrian scientist and Augustinian friar who laid the foundation of the science of heredity and genetics. Although his contributions to science were not widely recognized during his life, his work with pea plants in the mid-19th century revolutionized our understanding of how traits are inherited across generations, thus greatly influencing medicine, agriculture, and evolutionary theory.

Born in the small farming village of Hynčice in the former Austro-Hungarian Empire, now the Czech Republic, young Mendel was expected to work on the family farm, but showing early signs of academic talent, was encouraged to pursue further education. In 1843 he entered the Augustinian Abbey of St. Thomas in Brno. The monastery provided him with the opportunity to study science and cultivate his intellectual interests. Ordained as a priest in 1847, he continued to conduct his academic work in the monastery’s garden.

In 1856 he began his famous experiments with pea plants (Pisum sativum), cultivating over the course of eight years thousands of pea plants, crossbreeding them and meticulously recording the traits as they appeared in each generation. Because peas could easily be manipulated, he was able to self-pollinate or cross-pollinate them and study their color, shape, and configuration. His studies enabled him to explain how inherited traits are passed from one generation to the next through discrete units, now known as genes.

Carried on chromosomes, genes are segments of DNA that transmit the instructions for the development and functioning of an organism. One set of chromosomes is inherited from each parent. During reproduction, specialized cells called gametes (sperm and eggs) are formed and split in half, then reunite during fertilization. Accordingly, each offspring inherits a full set of chromosomes, half derived from each parent and thus constituting a unique combination.

Each gene exists in different versions. Some are dominant and some recessive. If dominant they express their effect even if only one of them is present, but two copies are required to be expressed if they are recessive. Both the dominant and recessive traits appear in future generations but may be transmitted in distinct species by different additional mechanisms, such as mutation or linkage. As the transmission of each gene occurs independently of the others, the members of the second generation will look different from the first.

Despite the significance of his discoveries, Mendel’s work went unnoticed during his life. His 1865 paper Experiments on Plant Hybridization did not receive widespread attention, and his work remained unknown in scientific circles. It was not until the turn of the twentieth century, over three decades after Mendel’s death, that his work was rediscovered by other scientists, marking a new era in genetics.