From which sequence does the Alu repeat originate from?
['The origin of Alu-derived minisatellites appears to have been mediated by short flanking repeats, as first proposed by Haber and Louis', 'Finally, we propose that the origin of Alu subfamilies in human populations may be related to evolution of chromosome Y.', 'Our analysis indicates that about 60 Myr ago, before the prosimian divergence, free left and right monomers formed an Alu heterodimer connected by a 19-nucleotide-long A-rich linker.', 'the presence of Alu-like structural motifs supports the hypothesis of the monophyletic origin of Alu and B1 repeats, i.e., from a common 7SL RNA-derived retroposing monomeric element', 'Alu elements are each a dimer of similar, but not identical, fragments of total size about 300 bp, and originate from the 7SL RNA gene.']
['The presence of Alu-like structural motifs supports the hypothesis of the monophyletic origin of Alu and B1 repeats, i.e., from a common 7SL RNA-derived retroposing monomeric element, The origin of Alu subfamilies in human populations may be related to evolution of chromosome Y.']
['7SL RNA']