A deficit in iron-sulphur cluster biogenesis is considered the primary effect of FXN deficiency, a notion supported by a number of studies showing that the activities of the iron-sulphur cluster-dependent aconitase and mitochondrial respiratory chain complexes I, II and III drastically reduce in tissues of FRDA patients8, 39, 40. The gene discussed is NDUFV1; the disease is Friedreich ataxia.