Any of a class of dispersed moderately repetitive DNA found in eukaryotes, consisting of numerous copies of relatively long (generally 6–8 kb) sequences scattered throughout the genome. LINEs are retrotransposons and can spread by reverse transcription: an RNA transcript is formed, then a DNA copy of this, which subsequently undergoes insertion into the genome. However, many have lost this ability to move about the genome and are in effect ‘molecular fossils’. In total LINEs account for about 20% of the human genome, of which most belong to the L1 family. These are 6 kb long and represent about 17% of the total human DNA. Active L1 LINEs contain two large coding regions plus noncoding flanking sequences. One of these encodes both an endonuclease and a reverse transcriptase.