FANCA and Friedreich ataxia: The similar sensitivity of FA cells from 21 groups (FANC-A, B, C, D1, D2, E, F, G, I, J, L, M, N, O, P, Q, R, S, T, U and V [2, 5, 6, 9–19]) to DNA crosslinking agents and the common clinical phenotype associated with each group suggest that the FA proteins all function in a common signaling transduction pathway (the FA pathway).