Hypothesis regarding the nature of the fragile X mutation. A reply to Winter and Pembrey

Pembrey et al. (1985) proposed a hypothesis regarding the nature of the fragile X [fra(X)] mutation. Recently they analyzed DNA linkage data (Winter and Pembrey 1986) that we and others have published on fra(X) pedigrees, found significant linkage heterogeneity, and modified their hypothesis to explain the observations. We would like to point out that their modified hypothesis is not supported by the data available.