Practice question

Insertion sequence IS elements represent simplest autonomous mobile DNAs approximately 0.7-2.5 kb encoding only transposase flanked by terminal inverted repeats typically 10-40 bp generating target site duplication upon insertion. Predominantly found in prokaryotic genomes including Escherichia coli, they serve as primary agents of spontaneous mutation, genome rearrangement, and composite transposon formation flanking antibiotic resistance genes. High copy number, low specificity, and ability to activate cryptic operons by insertion highlight IS elements as major drivers of bacterial adaptation, horizontal gene transfer, and evolution.