Barbara McClintock discovered a little thing called the transposable element in 1950

While everyone else was distracted by the structure of DNA, Barbara McClintock was discovering a little thing called the transposable element.

Barbara McClintock discovered a little thing called the transposable element in 1950
McClintock, B. 1950. The origin and behavior of mutable loci in maize. PNAS. DOI: 10.1073/pnas.36.6.344

For many years, scientists studied genetics but weren't entirely sure how it all worked on the molecular level.

They were aware of chromosomes, knew that they were composed of DNA and protein, but there was still a big question about the functional role of those two components in inheritance.

Fortunately for McClintock, who studied genetics in maize (corn), it didn't matter much what the genetic material was but that it could be tracked and its effects seen in the offspring of her crosses.

As an early cytogeneticist (scientist that studies chromosomes), McClintock developed many of the foundational techniques that were required for studying chromosomes in maize and she produced the first genetic maps of all 10 chromosomes.

Her early work was focused on studying inheritance and she was one of the first to observe and describe the phenomenon of homologous recombination, or crossing-over, which is when two chromosomes exchange genetic information.

She published this work in 1931 and continued to study maize genetics until her curious observation that pieces of chromosome 9 appeared to move around the genome.

But these pieces, Ac (activator) and Ds (inhibits pigment production), didn't just move around, Ac seemed to control Ds, and ultimately the color patterns of the maize kernels!

The figure above displays the kernels that McClintock described in, 'The origin and behavior of mutable loci in maize.'

Kernel 10 - no Ac, 11-13 - 1 copy of Ac, 14 - 2 copies, 15 - 3 copies.

We know today that 66% of the human genome and 85% of the maize genome is made up of these mobile 'transposable' elements and they are key in our understanding of epigenetics, but back in 1950, this discovery was problematic.

At the time, it was thought that genomes were static and ordered; pieces of them did not move around.

McClintock's findings were so poorly received that she stopped formally publishing them after 1953 because she thought her colleagues just weren't interested.

Fortunately, her work was 'rediscovered,' or, more accurately, 'understood,' in the 1970's when similar elements were found in bacteria, flies and humans.

She was awarded the Nobel in 1983 for the discovery of transposable elements, which was 3 decades after her original description of them.

McClintock's story in science isn't dissimilar from that of other prominent women, like Rosalind Franklin.

However, unlike Franklin, McClintock lived long enough to finally be properly recognized for her historic achievements.