Figure 4.

Model for the generation of L1 elements and their 3′-transduced regions in gi 3288437 and gi 2588627. Hop 2 (gi 3288437) and Hop3 (gi 2588627) are likely to be related descendants of the same Master L1 element. At least two, and possibly three (in case of gi 2588627) 3′-transducing intermediate transposition events would result in the structures seen at the DNA sequence level. The 31-bp sequence immediately downstream from the L1 is 100% identical between the two transduced segments, and in both cases is followed by a poly(A) tail. The proposed intermediates have not yet been found in the human genomic sequence available to date. The blue segment in Hop 3 reflects the possibility of two rather than one intermediate retrotransposition events between the master and Hop 3 elements, as there are two internal poly(A) sequences within the transduced segment.