Final answer:
A transposable element, or transposon, is a DNA segment capable of moving within a genome, discovered by Barbara McClintock in the 1940s during her maize genetics research.
Step-by-step explanation:
A transposable element, also known as a transposon or 'jumping gene', is a segment of DNA that can move around to different parts of a genome. These elements contain special inverted repeat sequences at their ends along with a gene that codes for the enzyme known as transposase. This enzyme is crucial for the element's ability to excise itself from one location in a DNA molecule and integrate into DNA at another location, a process known as transposition.
Transposable elements were first discovered by American geneticist Barbara McClintock in the 1940s during her research on maize genetics. She noted that these elements could move within a DNA molecule, altering phenotype by either inactivating or activating genes, thereby introducing genetic diversity. McClintock's pioneering work on transposons earned her recognition later in her career and is fundamental to our understanding of the genome's dynamic nature.