Theodosius Dobzhansky

In a previous thread, reader Istvan Albert mentioned about very good genetics book by Theodosius Dobzhansky. We did some google search on him and found a very good biographical memoir of him written by his student, who headed AAAS afterward.

Theodosius Dobzhansky was one of the most influential biologists of the twentieth century; he also was one of the most prolific. His first publication appeared in 1918 when Dobzhansky was eighteen years old. The complete list of his publications comprises nearly 600 titles, including a dozen books. The gamut of subject matter is enormous, and includes results of experimental research in various biological disciplines, works of synthesis and theory, and essays on humanism and philosophy, to name but three.

It is fascinating to find that Dobzhansky did everything from gene mapping to population biology in 1920s and 30s.

Dobzhansky also made significant contributions to “classical” genetics, particularly during the 1920s and 1930s. I shall mention but a few. Using translocations between the second and third chromosomes of Drosophila melanogaster, Dobzhansky demonstrated that the linear arrangement of genes based on linkage relationships corresponds to a linear arrangement of genes in chromosomes (1929). This linear correspondence had been postulated before, but proof was first provided by Dobzhansky (and independently by Muller and Painter in the same year). Also in 1929, Dobzhansky advanced the first sophisticated cytological map of a chromosomechromosome III of D. melanogaster. He showed that the relative distances between genes are different in the linkage and in the cytological map; genes clustered around the center of the linkage map are spread throughout a larger portion of the cytological map. He correctly inferred that the frequency of crossing over is not evenly distributed throughout the chromosome. Later he produced cytological maps of the chromosomes II (1930) and X (1932) of D. melanogaster, and propounded that the centromere (the “spindle fiber attachment” in the terminology of the time) is a permanent feature of chromosomes. He demonstrated that translocations decrease the frequency of crossing over and advanced a hypothesis to account for this reduction (1931). Dobzhansky demonstrated that the determination of femaleness by the X chromosome is not the result of a single or a small group of genes, but to multiple factors distributed throughout the chromosome (1931). His publications on the genetic and environmental factors affecting sex determination started in 1928 and continued for more than a decade.

These studies included work on bobbed mutants in the Y chromosome and their role in male sterility (1933), as well as numerous publications ongynandromorphs and “superfemales.” His publications concerning developmental genetics started in 1930 and continued for many years.

But, but, didn’t the field of genetics start with Watson and Crick? No, it started with Thomas Hunt Morgan. The second important researcher was Morgan’s student Alfred Sturtevant, who constructed the first genetic map of a chromosome in 1913. We wanted to say more about his research, but unfortunately the seminal paper is still not openly accessible after 100 years !!