Fig. 5.

Evolution of HeT-A sequences in the centromere region of the Y chromosome, deduced by Mendez-Lago et al. (45) (not to scale). The bottom diagram shows telomere sequence transposed into the Y chromosome: eight HeT-A elements (orange arrows) and one partial TART (#4; yellow arrow). Elements 1, 2, 3, and 5 are truncated HeT-As, and elements 6–9 are complete HeT-As. The top diagram shows 159 kb cloned in the sequenced BAC. The partial elements underwent complex amplifications to make up the 18HT satellite, which is partially represented by pentagons and black arrows on the left and is not further considered here. The end result of the several amplifications of the initially complete elements is shown on the right (numbering retained from ref. 45 to indicate origin of different parts of the sequence). Elements with two numbers result from amplifications of parts of two elements. Triangles, nontelomeric retrotransposons (copia, mdg1, diver, F, and 1731) that inserted at various times during the sequential amplifications of this DNA; green boxes, segment of autosomal region 42A transposed into element 8 and later duplicated. [Based on figure 7 in the work by Mendez-Lago et al. (45) and reproduced with permission from Oxford University Press.]