In the 19th century, it was commonly believed that an organism’s traits were passed on to offspring in a blend of characteristics ‘donated’ by each parent. Heredity was poorly understood in general, and the concept of a gene did not exist at all.
Austrian monk Gregor Mendel was unconvinced with traditional explanations of how traits were passed from one generation to another.
Between 1856 and 1863, Mendel decided to try and work out the principles of heredity himself, with the assistance of the humble garden pea (Pisum sativum L.).
Among the many species on which Mendel worked, he selected pea because the plants and seeds have a wide array of distinct features that occur in two easily identifiable forms (e.g. seed shape – round or wrinkled; plant height – tall or short).
The pea flower is another useful feature of these plants, since it ensures that the flowers of the hybridised and parent plants are protected from any foreign pollen. The relatively short growth period is another advantage; there was not a long wait for the results.
Over 8 years, Mendel studied pea traits one at a time and crossbred variants to systematically record how traits were passed on from one generation to the next: a mammoth task that involved approximately 28,000 pea plants.
Mendel’s study produced astonishing results and found very similar patterns of inheritance for all seven features he studied.
Mendel also identified a consistent mathematical formula that explained the frequency with which each trait appeared. He also observed dominant and recessive traits.
Despite the results being published in the “Proceedings of the Brunn Society for the Study of Natural Sciences” in 1866, Mendel’s work was widely ignored by the scientific community during his lifetime.
Before Mendel’s experiments on the garden peas, Thomas Andrew Knight (in 1799) and John Goss (in 1822), both from England, had carried out breeding experiments in the same plant.
When crossing plants yielding green peas with others yielding yellowish-white peas, Goss noted that, in the first generation, only yellowish-white peas were produced. Breeding from these hybrids, he was astonished to get three types of plants: one had only green peas, one only yellowish-white, and the third kind had both green and yellowish-white in the same pod.
Despite making some interesting observations, neither Knight nor Goss counted the number of peas with particular traits and consequently failed to discover the hereditary mechanism.
In 1900, three European botanists – Hugo De Vries (Holland), Carl Correns (Germany) and Erich Von Tschermak (Austria) were independently carrying out heredity research themselves and uncovered Mendel’s findings.
The new field of genetics was born and Mendel became regarded as the ‘father of genetics’, although the terms ‘gene’ and ‘genetics’ would be coined much later.
Mendel’s Legacy at the John Innes Centre
William Bateson, the first director of the John Innes in 1910, was a firm advocate of Mendel’s theory.
Bateson initially introduced ‘Mendelism’ to Britain, when he translated his paper into English in the early 20th century. Bateson further championed Mendel’s work when he gave a lecture in 1916 titled ‘15 years of Mendelism’.
Bateson would go on to coin the word ‘genetics’ and much of the discipline’s other terminology, then in 1910 the John Innes Institute became the first research institute devoted to Mendelian genetics in Britain, in which a programme of research was initiated to apply and test Mendel’s theory. This research became a launch pad for the start of a long history of pea research at the John Innes Institute.
Later research confirmed the gene (Mendel’s ‘factor’) as the unit of heredity and the chromosome as the physical structure which carried the genes. Additionally, exceptions to Mendel’s principles have been discovered as our knowledge of genes and inheritance has increased.
Work at the John Innes Institute has characterised Mendel’s genes at the molecular level, drawing on resources from our Germplasm Resource Unit, which houses over 3,500 variants of pea.