Barbara McClintock discovers "jumping genes"

Transposable elements (TE) are DNA sequences that “jump” from one location in the genome to another.  McClintock’s work not only showed that sequences can move, but also that this movement across the genome can create and reverse mutations as well as alter genome size, all during various stages of cell development.  McClintock conducted standard genetic self-breeding experiments causing broken chromosomes and noted unusual color patterns in the offspring, to understand the cause of this variety she compared the chromosomes of each generation with that of the parent and found that certain sections of the chromosomes had switched their position.  At first her discovery was met with skepticism because it went directly against the popular theory at the time that genes were fixed in their chromosomal position but McClintock’s work was rediscovered through work in bacteria a decade later and earned her a Nobel Prize in 1983.

• Original paper:  The origin and behavior of mutable loci in maize.

Supplementary paper:  Junk DNA as an evolutionary force