1. Yoder, J., Walsh, C. & Bestor, T. Trends Genet. 13, 335–340 (1997).
2. Henikoff, S. & Matzke, M. A. Trends Genet. 13, 293–295 (1997).
3. Waugh O'Neill, R. J., O'Neill, M. J. & Marshall Graves, J. A. Nature 393, 68–72 (1998).
4. Jiang, J.et al. Proc. Natl Acad. Sci. USA 93, 14210–14213 (1996).
5. Sun, X., Wahlstrom, J. & Karpen, G. Cell 91, 1007–1019 (1997).