Long interspersed nuclear elements class 1 (LINE1) is a type of transposable element, or “jumping gene,” that randomly copies and inserts itself into different genomic locations through reverse transcription (conversion of RNA into DNA). These active LINE1s can interrupt the genome through insertions, deletions, rearrangements, and copy number variations. LINE1 activity has contributed to the instability and evolution of genomes. As such, they are tightly regulated in the germline, however, they are controlled differently in apes and humans. LINE1 retrotransposons make up to ~17% of the human genome. While the majority are inactive in the human genome, there are roughly 80-100 that have retained the ability to retrotranspose with considerable variation between individuals.