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By far the most elegant substantiation of evolutionary theory, however, comes from genetics. Darwin had no idea how random variation occurs. Modern genetics and the study of DNA have provided an elegant answer to that question and makes a fascinating story in its own right. Genetics, of course, starts with Gregor Mendel, who spent his adult life as a monk at the Augustinian Abbey of St. Thomas in Brno, then in Austria, now in the Czech Republic. The Abbey sent him for two years to study at the University of Vienna where he was encouraged to study variation in plants. Upon his return he did just that with pea plants in the Abbey's garden. He found that when he used the pollen from pea plants with purple flowers to pollinate plants with white flowers that the resulting seeds did not produce plants with flowers of an intermediate color but were either purple or white. He did experiments with other traits of pea plant with similar findings. He proposed that inheritance comes in discrete packets. Further breeding experiment showed that in the progeny purple flowers were more frequent in a ratio of three to one. Purple was "dominant" over white.
Mendel studied 29,000 pea plants eventually so that his statistics were overwhelmingly convincing. He put all of this in a paper published in 1865, which was largely ignored during his lifetime.
Mendel's work was rediscovered around 1900 and confirmed by many scientists. William Bateson, a British scientist, is credited with suggesting the word "genetics" for the science of inheritance and the word "gene" soon came into use to describe the unit of inheritance.
Where genes resided in egg and sperm was still a mystery and took some time to unravel. The next great name in genetics is Thomas Hunt Morgan, born to a distinguished Kentucky family in 1866. His story is close to home because he obtained his Ph.D. at Johns Hopkins in 1890. His main work was carried out at Columbia University where he set up a laboratory to study inheritance in the fruit fly Drosophila. Fruit flies are easily maintained in the lab, have a two-week generation time, and have giant easily observed chromosomes in their salivary glands. This combination of characteristics allowed Morgan to show that genes reside in the chromosomes, structures that form in pairs when a cell begins to divide and which partition equally between the two daughter cells.
By studying mutant fruit flies, Morgan found that genes were arrayed in lines along chromosomes and started a new branch of genetics that establishes the order in which genes for specific characteristics exist along chromosomes. Such sophisticated research went on with little understanding of the underlying biochemistry of genes.
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