Fig. 1: General classification of repeats, the typical structure of TEs and TRs, and the proportion of various types of repetitive elements in the human genome.

Sub-graph (a): Classification of repeats in the human genome. Sub-graph (b): Arrangement and characterization of repeats in the human genome. Sub-graph (c): Typical structure of DNA transposons, in which TIR and TSD respectively represent the terminal inverted repeat and target site duplication. Sub-graph (d): Typical structure of non-LTR retransposons, in which the color blocks represent the protein domains contained in each family, and the gray block represents the non-coding regions. Sub-graph (e): Typical structure of retrovirus-like LTR retrotransposons, in which LTR represents the long terminal repeat. Sub-graph (f): Typical structure and distribution of TRs in the human genome. Sub-graph (g): Proportion of TRs and active TEs in the human genome. Specifically, LINE-1 and LINE-2 retransposons are represented by L1 and L2 respectively, while SINE-VNTR-Alu retrotransposon and Mammalian-wide interspersed repeats are represented by SVA and MIR. The color arrows represent the repetitive unit (or motif) of each kind of TR, and the light black structure represents the chromosome.