Alu elements

Definition: 

A type of primate-specific transposable element, or “jumping gene,” that is roughly 300 base pairs long and exists in large copy number across all chromosomes of primate genomes (over 1 million copies in the human genome). Alu elements are also called Short Interspersed Elements (SINEs). They lack the ability to copy and paste themselves directly, but are able to “hitchhike” via the activity of Long Interspersed Elements (LINEs) that have retained the ability to copy and paste. Alu elements were considered to be a part of what has been called “junk DNA” because they do not code for the production of proteins, however they may serve some yet unknown function and definitely contribute to genomic plasticity, evolution, and disease.