Last updated: April 22, 2013
1865: Mendel's Peas
Gregor Mendel describes his experiments with peas showing that heredity is transmitted in discrete units.
From earliest time, people noticed the resemblance between parents and offspring, among animals and plants as well as in human families. Gregor Johann Mendel turned the study of heredity into a science.
Mendel was a monk in the Augustinian order, long interested in botany. He studied mathematics and science at the University of Vienna to become a science teacher. For eight years, starting in 1857, he studied the peas he grew in the garden of his monastery. He carefully pollinated the plants, saved seeds to plant separately, and analyzed the succeeding generations.
He self-pollinated plants until they bred true - giving rise to similar characteristics generation after generation. He studied easily distinguishable characteristics like the color and texture of the peas, the color of the pea pods and flowers, and the height of the plants.
When he crossed true-breeding lines with each other, he noticed that the characteristics of the offspring consistently showed a three to one ratio in the second generation. For example, for approximately every three tall plants, one would be short; for about every three plants with yellow peas, one would have green peas. Further breeding showed that some traits are dominant (like tall or yellow) and others recessive (like short or green). In other words, some traits can mask others. But the traits don't blend: they are inherited from the parents as discrete units and remain distinct. Furthermore, different traits - like height and seed color - are inherited independently of each other.
Mendel read his paper, "Experiments in Plant Hybridization" at meetings on February 8 and March 8, 1865. He published papers in 1865 and 1869 in the Transactions of the Brunn Natural History Society.
Some Biographies of Mendel:
Iltis, Hugo, Life of Mendel. Eden and Cedar Paul, trans. London: George Allen & Unwin Ltd. 1932. From the German publication, "Gregor Johann Mendel, Leben, Werk, und Wirkung", Berlin: Julius Springer, 1924.
Orel, Vitezslav, Gregor Mendel: The First Geneticist. Oxford & London: Oxford University Press, 1996.
In the following paper, scientists explained, in molecular detail, the cause of the wrinkled seed trait that Mendel had observed in his peas:
Bhattacharyya M.K., Smith A.M., Ellis T.H., Hedley C., and Martin C.. The wrinkled-seed character of pea described by Mendel is caused by a transposon-like insertion in a gene encoding starch-branding enzyme. Cell, 60: 115-122, 1990.