On the cover: Anticipation is the phenomenon by which a genetic
condition appears earlier and with increased severity in
succeeding generations. This phenomenon was first described in
myotonic dystrophy (MD) by Fleischer in 1918 (Archiv für
Ophthalmologie, Berlin, 96, 91–133), but it remained a
controversial subject for many years thereafter. In 1948,
Penrose (Annals of Eugenics, 14, 125–132) devised a theoretical
explanation for anticipation; he proposed that the reverse
relationship between the degree of anticipation and the
correlation between parent and child age of onset was actually a
sampling artefact. In 1989, Höweler et al. set out to test this
theory and, without bias, found an earlier age of onset in
children than in parents with MD (Brain, 112, 779–797),
supporting the phenomenon of anticipation. In 1992, three groups
reported the genetic basis of MD to be expansion of a
trinucleotide repeat (Cell, 68, 799–808; Science, 255,
1253–1255; Science, 255, 1256–1258), conclusively explaining
anticipation