More to Explore 87
Over six years of work, Mendel found the same pattern in every crossbreeding experiment he tried. In the second generation, one plant in four switched and showed the recessive
trait (the trait that hadn’t showed up at all in the first generation). Always three to one.
He knew that a plant inherited one version of each trait (or gene) from father and
mother plants. But what if, in each pairing of traits, one trait were always stronger (dominant), and one always weaker (recessive)? Then, when the traits mixed, a first-generation
plant would always show the dominant one (all yellow, or all tall).
But three to one . . . . That happened in the second generation. Mendel realized simple
mathematical probability said there could be four possible combinations of traits in a second-generation plant (either dominant or recessive trait from either father or mother plant).
In three of those combinations at least one dominant trait would be present, and that would
dictate what the plant became. In only one combination (recessive trait from both parents)
would there be nothing but recessive traits present. Three to one.
Traits did not mix. They were inherited from generation to generation and appear only
when they are dominant in an individual plant. Traits from countless ancestors flow into
each of us, in separate packages called “genes,” unblended for us to pass on even if a trait
doesn’t “show” in our generation.
It was not until 1900 that another scientist—Dutchman Hugo de Vries—realized the
scientific value of Mendel’s great gift to the world with his insights on heredity.
Fun Facts: Gregor Mendel’s concept of heredity required two parents.
Dolly the sheep made scientific history in 1997 when she was created
from the cells of a single adult sheep in a Scottish lab. She was cloned, an
exact genetic duplicate of her mother, with no contributing gene cells
from a father.
More to Explore
Bankston, John. Gregor Mendel and the Discovery of the Gene. Hockessin, DE:
Mitchell Lane, 2004.
Bardoe, Cheryl. Gregor Mendel: The Friar Who Grew Peas. New York: Abrams
Books for Young Readers, 2006.
George, Wilma. Gregor Mendel and Heredity. Wayland, England: Howe Publishers,
1995.
Gribben, John. Mendel in 90 Minutes. London: Constable Press, 1997.
Haven, Kendall. Marvels of Science. Englewood, CO: Libraries Unlimited, 1995.
Henig, Robin. The Monk in the Garden: The Lost and Found Genius of Gregor Mendel. New York: Houghton Mifflin, 2000.
Yannuzzi, Della. Gregor Mendel: Genetics Pioneer. New York: Franklin Watts, 2004.