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Structure of direct duplications of U3 sequences in the U3 LTR. U3 is indicated by white boxes with vertical black bars; R is indicated by black boxes; U5 is shown by white boxes with horizontal black bars. Direct duplications are indicated by white arrows, and the sizes of the duplications are shown. The detailed sequences at the junctions are shown in white boxes, and microhomologies are indicated by bold letters. Normal target duplications are indicated by black arrows.
