1983

Plant Genetics

Gregor Mendel (1822–1884), Barbara McClintock (1902–1992)

Genes—the fundamental units of inheritance in all forms of life on Earth—were essentially discovered in the late nineteenth century by Austrian botanist Gregor Mendel. While Mendel did not have the technological tools to visualize actual genes, he deduced their presence by a series of clever experiments on pea plants between 1856 and 1863. By carefully following the expression of various traits such as seed and flower color and plant height, he was able to show that inherited traits could be dominant or recessive, and that a series of rules of heredity could be used to predict the traits of offspring from the known traits of parents. While not recognized as such at the time, Mendel is now widely regarded as the founder of modern genetics.

Among the most important early advances in genetics in the twentieth century was the ability to finally visualize individual chromosomes, the carriers of the DNA inside cells. Some of the most important early discoveries in this field were made by American botanist and geneticist Barbara McClintock, who studied the chromosomes of maize (corn) from the late 1920s to the early 1950s. McClintock developed novel microscopy methods to directly observe changes in chromosomes during cell division and to characterize the roles that different parts of the chromosome play in transmitting genetic information to offspring. She was among the first to advocate that parts of the DNA structure could control, or regulate, the expression of certain genes or genetic traits. The idea was not understood or accepted by her contemporaries, however. Many of her concepts were ultimately vindicated in the 1960s and 1970s as even more advanced technology provided the molecular evidence in support of her hypotheses.

Like Mendel (who was an Augustinian friar), McClintock did her painstaking observational research mostly in solitude, and was not widely recognized for her contributions at the time. However, unlike Mendel, she was ultimately recognized in her lifetime, receiving the Nobel Prize in Physiology/Medicine in 1983 for her early genetics work. That same year, a popular biography of McClintock (A Feeling for the Organism, by E. F. Keller) was published, helping to further bring her critical contributions to genetics to light.

Main image: Plant geneticist Barbara McClintock in her laboratory in 1947. McClintock made important discoveries about the ways that genes are responsible for switching the physical traits of an organism on or off. Inset: A 2008 photo of a variety of plant chromosome pairs from the science museum in South Kensington, London.