The American zoologist and geneticist Thomas Hunt Morgan (1866-1945) established the theory of the gene which helped clarify the process of evolution and formed the modern basis of heredity.
Morgan formed the Chromosome Theory of Heredity after his fruit fly experiment. He was proven correct in his assumptions that chromosomes contain many genes, and that some chromosomes are related to sex. He also proved that genes on one chromosome were inherited together, and genes on different chromosomes were not. He noticed that there were no exceptions to his general rule. He formulated three laws that go with his theory of heredity:
- Genes are inside of chromosomes. A certain gene is at the same spot on each chromosome, and that spot is called the locus.
- Crossing Over, or the subtle exchange of fragments of chromosomes, only takes place between homologous chromosomes.
- The frequency of a cross-over is directly in proportion to how far apart the chromosomes are in the cell nucleus. The farther apart they are, the more they cross over.
Morgan basically was the man who figured out what genes were, without knowing about DNA. He published many papers and books. Morgan was "the man who made it happen." Mendel had laid the groundwork for someone like Thomas Hunt Morgan to come in and set genetics in motion.
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