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the duplicated chromosomes

Mendel chose seven different characters to study. The word character in this regard means a specific property of an organism; geneticists use this term as a synonym for characteristic or trait.

For each of the characters that he chose, Mendel obtained lines of plants, which he grew for two years to make sure that they were pure. A pure line is a population that breeds true for (shows no variation in) the particular characterbeing studied; that is, all offspring produced by selfing or crossing within the population are identical for this character. By making sure that his lines bred true, Mendel had made a clever beginning: he had established a fixed baseline for his future studies so that any changes observed subsequent to deliberate manipulation in his research would be scientifically meaningful; in effect, he had set up a control experiment.

Two of the pea lines studied by Mendel bred true for the character of flower color. One line bred true for purple flowers; the other, for white flowers. Any plant in the purple-flowered line—when selfed or when crossed with others from the same line—produced seeds that all grew into plants with purple flowers. When these plants in turn were selfed or crossed within the line, their progeny also had purple flowers, and so forth. The white-flowered line similarly produced only white flowers through all generations. Mendel obtained seven pairs of pure lines for seven characters, with each pair differing in only one characte