18 SINEs and LINEs: Troublemakers, Saboteurs, Benefactors, Ancestors

摘要: We will never know whether the world is better or worse for viruses, mosquitoes, protozoan pathogens, poison ivy, raptors, retroposons. must take natural leave it; we cannot pick and choose. But if could choose, retroposons would be a tough call, because they have given much, taken much away. Thanks to human genome project, now that almost half of squandered on (SINEs, LINEs, retroviral-like elements), fact can regard as humbling, puzzling, amazing, but certainly nothing proud of. On other hand, good case made contributed richly genomic diversification in DNA World, are most likely not newborn saboteurs benefactors molecular fossils transitional genomes enabled RNA World turn into World. THE REVERSE FLOW OF GENETIC INFORMATION FROM INTO The earliest hints information might flow back were discoveries (1) major family interspersed repeated sequences was about 300 bp long, exhibited 14% average sequence divergence, typically contained nearly central Alu restriction site—hence name elements (Houck et al. 1979); (2) homologous an abundant, homogeneous, small cytoplasmic then unknown function called 7S (Weiner 1980); (3) many strong polymerase III transcription units, at...