Biology  5/e   Raven/Johnson
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"Her mother's eyes, her father's nose" etc., are attributed to our children soon after birth. Similarities from generation to generation have been observed in all familiar plants and animals for centuries. However intriguing the similarities were, the causes of the similarities eluded humankind for a long time. Faulty beliefs were abundant. Even well controlled experiments failed to reveal the secrets of inheritance.

It was Gregor Mendel who built on earlier work and improved on the earlier methods that formed the foundation of the scientific study of inheritance. Mendel added the key step in the experimentation--quantification. His records of variations of phenotypes resulting from various crosses enabled him to create a model upon which understanding of heredity would be built. He established the Law of Segregation and the Law of Independent Assortment. Mendel also developed the procedure known as the testcross. Reginald C. Punnett added his visualization device, the Punnett square. Eventually it was recognized that chromosomes were the bearers of hereditary information and the "factors" of Mendel were genes. The recognition of the genetic effects of gene cross-over led to the ability to map chromosomes. Mechanisms of gene interaction were discovered that shed light on phenomena that had not yielded to more simple models.

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