In the Fanconi anemia complementation group A (Fanca) and Fanconi anemia complementation group G (Fancg) deficient mice, whose Fancd2 activation and FA/Brca1 pathway functionality are abolished, the neuron number is reduced at the dorsal telencephalon 32,49. The gene discussed is BRCA1; the disease is Fanconi anemia complementation group I.