SIM and CIM to identify QTLs for conditioned fear expression in the BXD mouse GRP. A, BXD panel shows continuous variation in fear expression as assessed by the percentage of time strains spent freezing in response to the CS in the testing context. Data are shown as means ± SEM. Parental strains are shown in black (B6) and white (D2). The F1 cross (B6D2F1) and 62 BXD strains are shown in gray. B, SIM reveals a significant QTL (LRS > 21.70) on Chr 13 (peak LRS at 84.65 Mb), a highly suggestive QTL (LRS = 20.67) on distal Chr 13 (peak LRS at 118.39 Mb), and two suggestive loci (LRS > 13.68) on Chr 10 and Chr X. C, CIM controlling for QTL 13a using marker mCV24625340 reveals an additional suggestive QTL on Chr 11 (peak LRS at 13.57 Mb). D, Candidate protein-coding genes listed in order of location on each on each chromosome and selected based on evidence of involvement in human neurological disorders or key phenotypes related to fear and anxiety, learning and memory, or anxiety and mood disorders. Bolded genes are of special interest based on meeting both criteria or evidence of involvement in conditioned fear or anxiety disorders. “&” indicates genes with no known single-nucleotide polymorphisms (SNPs) between the parental strains.