Potter SS, Brorein Jr. WJ, Dunsmuir P, Rubin GM. Transposition of elements of the 412, copia and 297 dispersed repeated gene families in Drosophila. Cell. 17: 415-427. 1979.
This paper was the first molecular demonstration of the presence of transposable elements, or jumping genes, in metazoans. The sequences of a couple of transposable element families had been previously cloned by members of the Hogness Lab. They did in situ hybridizations to the polytene chromosomes of Drosophila salivary glands and saw some differences in hybridization positions, but interpreted this to be the result of variations in polytenization of chromosomes in different strains, and not to reflect genuine differences in chromosome positions (See their Cold Spring Harbor paper of 1978).
In this paper we cloned “empty-filled” corresponding DNA sites from different Drosophila, showing that in some cases the site would have a transposable element and in other cases not. This clearly showed they could move about the genome. We also used reassociation kinetics to show that the copy number of the elements could dramatically increase in tissue culture cells, showing that in this situation the elements were de-repressed and moved and replicated like crazy. These results showed that the puzzling moderately repetitive fraction of DNA was in fact made up of jumping genes.
I was Gerald Rubin’s second postdoc. He went on to do rather well.