Axons/physiology; Cerebral Cortex; Gene Expression Regulation, Developmental/genetics; Homeodomain Proteins/genetics; Mutation/genetics; Phenotype; Thalamus; Transcription Factors/genetics; Alkylating Agents/pharmacology; Animals; Body Patterning/drug effects; Body Patterning/genetics; Cell Adhesion Molecules, Neuronal/genetics; Cell Adhesion Molecules, Neuronal/metabolism; Cerebral Cortex/embryology; Cerebral Cortex/growth & development; Cerebral Cortex/metabolism; Embryo, Mammalian; Ethylnitrosourea/pharmacology; Extracellular Matrix Proteins/genetics; Extracellular Matrix Proteins/metabolism; Female; Gene Expression Regulation, Developmental/drug effects; Genetic Testing/methods; Lac Operon/genetics; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Transgenic; Nerve Tissue Proteins/genetics; Nerve Tissue Proteins/metabolism; Neural Pathways/abnormalities; Neural Pathways/embryology; Neural Pathways/growth & development; Reelin Protein; Serine Endopeptidases/genetics; Serine Endopeptidases/metabolism; Thalamus/embryology; Thalamus/growth & development; Thalamus/metabolism; beta-Galactosidase/metabolism