A transposon is a mobile genetic element that can insert itself into new positions within the genome of its host organism. Transposons were first described in maize by Barbara McClintock in the 1940s, and are sometimes referred to as “jumping genes”. Most transposons are flanked by short direct repeats of DNA sequence, which are used by the transposon for insertion into new genomic sites.
Transposons are found in all kinds of organisms, from bacteria to plants to animals. In fact, it is estimated that more than half of the human genome consists of transposable elements! Transposons can cause mutations and other changes in the genome, which can be beneficial or harmful to the organism. For example, some plant diseases are caused by transposons that insert themselves into genes and disrupt their function. On the other hand, some helpful traits, such as resistance to disease or tolerance to environmental stressors, have arisen due to advantageous transposon insertions.
There are several different types of transposons, including retrotransposons (which use RNA as an intermediate), DNA transposons (which directly insert themselves into new genomic sites), and hATs (hybridization-activated transcription factors). Retrotransposons are further divided into long terminal repeat retrotransponson (LTR) and non-LTR retrotransponson subtypes. LTR retrotransponson contain two copies of flanking sequences called long terminal repeats (LTRs), while non-LTR retrotransponson lack these flanking sequences. DNA transponson can be either autonomous or nonautonomous; autonomous DNA transponson carry their own genetic information for insertion into new sites, while nonautonomous DNA tranpsosn rely on enzymes encoded by other genes for their movement. hATs consist of a protein complex that binds to specific regulatory sequences in DNA and promotes transcription of nearby genes; hAT activity often results in chromosomal rearrangements.
While most mobile elements are selfish entities that increase their own chances of being passed on to future generations at the expense of the host organism’s fitness, there are also examples of altruistic mobile elements known as groupies. Groupies help stabilize genomes by repairing double-strand breaks or damaged telomeres; they may even confer benefits such as enhanced heat tolerance or protection against viral infections. Some researchers believe that groupies could be harnessed for therapeutic purposes – for example, to repair damaged tissue in patients with degenerative diseases like Alzheimer’s or Parkinson’s disease.