Post Mendelian Era ~1910-1920

While G.N. Collins was working with hybrids during 1912, he showed that the two characteristics known as ‘colorless aleurone’ and ‘waxy endosperm’ were inherited together most of the time. The issue with this ‘genetic linkage’ was that is was a contradiction of Mendel’s Law. The part that Collins’ observation disagreed with was that different characteristics are inherited differently. With this new found insight, the search for genetic linkages proved to be a very useful tool in constructing genetics maps and studying inherited medical conditions.

In 1913 Alfred Sturtevant joined Thomas Hunt Morgan to study Drosophila, a type of small flies and make what we call the first genetic map. They studied linkages between various genes. The proposal that they made was that genes that are closer together are less likely to separate during the process of ‘crossing-over’. Alfred made calculations of the percentages of crossing-over between the traits of the fly and came to the conclusion that the average distance between six sex-linked genes on the X-Chromosome.

During the time before World War I, about 1915, J.B.S. Haldane was working at his home in Oxford with his sister Naomi.  He showed that the traits of pink eyes and albino coloring in mice are linked, supposedly because the genes that carried those traits were in close quarters and on the same chromosome. The importance of this discovery was that it is the first demonstration of traits being genetically linked in a mammal. Interestingly Haldane wrote his final draft for the paper ‘Journal of Genetics’ while he was in the trenches of Flanders.

Charles Darwin and Gregor Mendel both published very controversial papers for their time, but never really linked together. Until Ronald Fisher made the link in 1918. The article he wrote on it was titled ‘The Correlation Between Relatives on the Supposition of Mendelian Inheritance’. Fisher’s paper ended up being one of the documents that started the study of population genetics, appropriately too because it demonstrated the continuous variations in traits like height can be understood from Mendelian principles.

Although not a humongous event, the founding of the Genetical Society still had its role in history. It was June 25th 1919 when William Bateson gathered a group of various geneticists and agreed to start what he called the Genetical Society, which was later renamed ‘The Genetics Society’.  With that society being founded, it also marks the end of the second decade of Post Mendelian genetic history.


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