Chapter 8 Morgan and Linkage

1933/morgan-bio.html Thomas Hunt Morgan was a famous geneticist who, in the initial years of the 20th century, studied Drosophila, the fruit fly, in his lab at New York City’s Columbia University. Morgan’s choice of Drosophila was both fortuitous and prescient not only for his own historic findings but also for developing a model organism that has evolved into a major workhorse in the science of genetics. These tiny flies reproduce quickly and leave a large number of progeny. Mendel had to wait months to plant and harvest two generations of peas. Morgan could study half a dozen generations in the same time. Moreover, Drosophila have only three chromosomes. Two of Morgan’s many findings stand out. Despite all the complicated looping of the DNA around chromosomal proteins, Morgan found that the genes on a chromosome have a remarkable statistical property –namely, mathematically genes appear as if they are linearly arranged along the chromosome. Thus, one can draw a schematic of a chromosome as a single strait line, with the genes in linear order along that straight line, even though the actual physical construction of the chromosome is a series of looped and folded DNA. Morgan’s second finding was no less important. He discovered that chromosomes recombine and