The chd7 mutant line (chd7ncu101/) has previously been characterized to have variable phenotype penetrance,19 similar to the heterogeneous disorder it models, CHARGE syndrome.51–53 In this analysis, we found that medium type largely increased behavioral variance between wild types rather than heterozygotes and mutants, a finding that highlights how embryo media might mask some mutant phenotypes. The gene discussed is CHD7; the disease is CHARGE syndrome.