AP BIOLOGY

Detailed explanation-1: -Since McClintock’s discovery, three basic types of transposons have been identified. These include class II transposons, miniature inverted-repeat transposable elements (MITEs, or class III transposons), and retrotransposons (class I transposons).

Detailed explanation-2: -DNA transposons move using a cut-and-paste mechanism [6]. In contrast, retrotransposons move in a copy-and-paste fashion by duplicating the element into a new genomic location via an RNA intermediate [7]. Thus, retrotransposons increase their copy number more rapidly than DNA transposons.

Detailed explanation-3: -Both class 1 and class 2 TEs can be either autonomous or nonautonomous. Autonomous TEs can move on their own, while nonautonomous elements require the presence of other TEs in order to move.

Detailed explanation-4: -Transposable elements (TEs), also known as “jumping genes” or transposons, are sequences of DNA that move (or jump) from one location in the genome to another. Maize geneticist Barbara McClintock discovered TEs in the 1940s, and for decades thereafter, most scientists dismissed transposons as useless or “junk” DNA.