Final answer:
Barbara McClintock discovered transposable elements, also known as 'jumping genes', in maize over 50 years ago, which can move within an organism's genome. This discovery, initially met with skepticism, eventually earned her a Nobel Prize and has had a profound impact on the field of genetics.
Step-by-step explanation:
The discovery of transposable elements that cause unstable mutations in maize was made over 50 years ago by Barbara McClintock while she was working on maize genetics. Her groundbreaking work introduced the concept of 'jumping genes', which are segments of DNA that can move within the genome and influence gene and protein expression. Initially met with skepticism, this discovery was later confirmed with the identification of transposons in bacteria and other organisms, earning McClintock the Nobel Prize in Physiology or Medicine in 1983.
McClintock's studies on the coloration of maize kernels led her to discover the Ds (dissociation) and Ac (activator) genes, which she found could move and cause chromosomal breakages and mutations. This understanding was crucial in the development of modern genetic theories, despite the fact that molecular technologies such as gene cloning and DNA sequencing were not available at the time of her research.
Overall, Barbara McClintock's work on transposable elements radically changed our understanding of genetics and her insights into epigenetic inheritance and gene regulation continue to influence scientific research today.