interspersed in the human genome as well as other animals. The Hobo transposons in Drosophila have been extensively studied due to their ability to cause gonadal dysgenesis. The insertion and subsequent expression of hobo-like sequences results in the loss of germ cells in the gonads of developing flies. Bacteria Bacterial transposons are especially good at facilitating horizontal gene transfer between microbes. Transposition facilitates the transfer and accumulation of antibiotic resistance genes. In bacteria, transposable elements can easily jump between the chromosomal genome and plasmids. In a 1982 study by Devaud et al., a multi-drug resistant strain of Acinetobacter was isolated and examined. Evidence pointed to the transfer of a plasmid in to the bacterium, where the resistance genes were transposed in to the chromosomal genome. Genetic diversity Transposons may have an effect on the promotion of genetic diversity of many organisms. DNA transposons can drive the evolution of genomes by promoting the relocation of sections of DNA sequences. As a result, this can alter gene regulatory regions and phenotypes. The discovery of transposons was made by Barbara McClintock who noticed that these elements could actually change the color of the maize plants she was studying, providing quick evidence of one outcome from transposon movement. Another example is the Tol2 DNA transposon in medaka fish that is said to be the result of their variety in pigmentation patterns. These examples show that transposons can greatly influence the process of evolution by rapidly inducing changes in the genome. Inactivation All DNA transposons are inactive in the human genome. Inactivated, or silenced, transposons do not result in a phenotypic outcome and do not move around in the genome. Some are inactive because they have mutations that affect their ability to move between chromosomes, while others are capable of moving but remain inactive due to epigenetic defenses, like DNA methylation and chromatin remodeling. For example, chemical modifications of DNA can constrict certain areas of the genome such that transcription enzymes are unable to reach them. RNAi, specifically siRNA and miRNA silencing, is a naturally occurring mechanisms that, in addition to regulating eukaryotic gene expression, prevents transcription of DNA transposons. Another mode of inactivation is overproduction inhibition. When transposase exceeds a threshold concentration, transposon activity is decreased. Since transposase can form inactive or less active monomers that will decrease transposition activity overall, a decrease in the production of transposase will also occur when large copies