Chromosome theory of heredity

In 1902, Walter Sutton and Theodor Boveri were able to show that the Mendelian characters (the genes) are physically carried by chromosomes (the chromosome theory of heredity), and the study of meiotic divisions and gametogenesis proved that Mendel s hypotheses were absolutely correct, so much so that they could be regarded no longer as hypotheses but as experimental realities. Mendel s laws gave a direct support to the conclusions that Darwin had obtained from the breeders. Every individual is indeed unique, because the recombination of its genes is a totally random process. 

The rediscovery of Mendel s laws, the demonstration of crossing-over, the chromosome theory of heredity, the link between sex and XX or XY chromosomes, and the discovery of the first Mendelian disorders in man (alcaptonuria and brachydactyly) were all obtained in the first ten years of the twentieth century. In that brief period of time, light was thrown on the millennial mystery of heredity, and genetics became a science. 

Bridges C.B. 1916. Non-disjunction as proof of the chromosome theory of heredity. Genetics 1 1-52. 

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