Nonviral retroposons: genes, pseudogenes, and transposable elements generated by the reverse flow of genetic information.

PERSPECTIVES AND SUMMARY . 632 THE AMAZING VARIETY OF RETROPOSONS "......... 635 The Viral Supeifamily 635 The Nonviral Superfamily "......... 636 RETROPOSONS DERIVED FROM PROCESSED MESSAGES 637 Processed Retropseudogenes .. . . . . ... . . . . . . .. . .. . . . . ..... . . . . ...... . . . ""'''''''''''''''''''''' 637 A Functional Semiprocessed Retrogene " "......... 640 LINES (LONG INTERSPERSED REPEATED SEQUENCES) ........ . "......... 641