Gregor Mendel

Gregor Johann Mendel (20 July 1822 – 6 January 1884) was an Austrian Empire biologist, meteorologist, mathematician, Augustinian friar and later abbot of St Thomas’s Abbey in Brno. Born into a Sudeten German family in Austrian Silesia, in what is today the Czech Republic, he is posthumously recognised as the founder of modern genetics. His systematic experiments on the garden pea between 1856 and 1863 established the fundamental principles of inheritance, later formalised as the laws of Mendelian genetics. Although his discoveries were overlooked during his lifetime, they were rediscovered around 1900, revolutionising biological science.

Early Life and Education

Mendel was born in Hynčice (then part of Austrian Silesia), the son of Anton and Rosine Schwirtlich Mendel. The family farm had been in their possession for over a century, and Mendel’s early years were shaped by agricultural work and gardening. He also developed an interest in beekeeping. Gregor had two sisters, Veronika and Theresia, the latter later assisting him financially by contributing her dowry to support his education.
He attended the Gymnasium in Troppau, where illness forced intermittent periods of absence. Between 1840 and 1843 he studied philosophy and physics at the Philosophical Institute of Palacký University in Olomouc, again facing both financial and health challenges. The monastic life offered security and educational opportunities unobtainable to a struggling farmer’s son, and when he joined the Order of Saint Augustine he took the name Gregor.

Academic and Monastic Career

At Olomouc, Mendel came under the influence of Johann Karl Nestler, a scholar of hereditary traits in plants and animals. Upon the recommendation of the physicist Friedrich Franz, Mendel entered St Thomas’s Abbey in Brno, where he trained as a priest. He worked as a substitute secondary school teacher but failed the oral component of the certification examinations in 1850.
To strengthen his academic foundation, Mendel studied at the University of Vienna from 1851 to 1853 under the sponsorship of Abbot Cyril Napp. His teachers included the physicist Christian Doppler, whose scientific rigour influenced Mendel’s methodological approach. Returning to Brno, Mendel taught physics and deepened his interest in natural science. A meeting in 1854 with the naturalist Aleksander Zawadzki further stimulated his research interests.
Mendel again attempted but failed the teacher certification exam in 1856. In 1862 he travelled to Paris and London, visiting major scientific exhibitions and institutions. The following years saw him rise within the abbey; in 1867 he succeeded Napp as abbot. Increasing administrative duties, including a protracted dispute over taxation imposed on religious institutions, curtailed his scientific work. Mendel died in Brno in 1884 from chronic nephritis. At his funeral, the composer Leoš Janáček played the organ. A later exhumation in 2021 provided additional biographical information, including genetic traits indicating predisposition to heart disease.

Experiments on Plant Hybridisation

Mendel’s seminal research was conducted in the abbey’s experimental garden. Assisted in concept by Zawadzki, though discouraged at times by senior clergy, he embarked on a systematic study of variation in pea plants (Pisum sativum). After preliminary trials with various plants, he selected seven traits that appeared to assort independently: seed shape, seed colour, seed-coat tint, pod shape, unripe pod colour, flower position, and plant height.
From 1856 to 1863 Mendel cultivated and examined around 28,000 pea plants. His experimental method involved crossbreeding true-breeding varieties, observing the first filial (F₁) and then the second filial (F₂) generations. For example, crossing true-breeding yellow and green peas yielded exclusively yellow seeds in the F₁ generation, but the green trait reappeared in the F₂ generation in a 1:3 ratio. Mendel explained this through the concepts of dominant and recessive traits, proposing that inheritance was governed by discrete factors—now known as genes.
From his experiments he formulated two fundamental principles:

• Law of Segregation: Each organism carries two factors for each trait, which segregate during gamete formation so that each gamete carries one.
• Law of Independent Assortment: The inheritance of one trait is generally independent of the inheritance of another, provided the genes lie on different chromosomes or are far apart on the same chromosome.

His 1866 publication, Experiments on Plant Hybridization, revealed the predictable patterns governing heredity. The full genetic basis of his observations became clear gradually and was completed only in 2025 with the identification of the final Mendelian genes in the pea genome.

Initial Reception and Legacy

When Mendel presented his findings to the Natural History Society of Brno in February and March 1865, they attracted modest local attention but were widely misunderstood. The scientific community largely overlooked his 1866 paper, interpreting it as a contribution to hybridisation rather than heredity. It received only a handful of citations in the subsequent decades. Even Charles Darwin, developing his theory of evolution through natural selection, remained unaware of Mendel’s work. Had Darwin accessed Mendel’s results, the integration of genetics with evolutionary biology might have occurred much earlier.
Correspondence with the eminent biologist Carl Nägeli also failed to yield recognition; Nägeli misunderstood the significance of Mendel’s findings. Despite this, Mendel reportedly remained confident that posterity would appreciate his work, remarking, “My time will come.”

Rediscovery and Impact on Modern Genetics

Around 1900, Mendel’s laws were independently rediscovered by Hugo de Vries, Carl Correns and Erich von Tschermak, each of whom verified aspects of his experimental results. Their rediscovery ignited the rapid development of the new science of genetics, providing a mechanistic explanation for inheritance and supporting the particulate model of heredity over the long-held theory of blending inheritance.
Early twentieth-century researchers integrated Mendelian principles with cytological observations of chromosomes, forming the chromosomal theory of inheritance. Quantitative genetics later explained traits influenced by multiple genes, reconciling Mendelian inheritance with continuous variation observed in nature. Mendel’s discoveries now form the foundation of classical genetics, molecular biology, plant and animal breeding, and modern evolutionary theory.