Growth retardation of fit1 mutants. (A) Representative fit1 mutants, each expressing one of the five fit1 alleles, shown with one wild-type littermate (far right). The genotypes of the mice, beginning at the left, are: c fit1^4397SB/c^26DVT; c fit1^494SB/c^26DVT; c fit1^764SB/c^26DVT; c fit1^3452SB/c^26DVT; c fit1^4226SB/c^26DVT; and c^ch +/c^26DVT. All mice shown are 26 days old. The wild-type littermate is from the mating that generated the fit1^494SB mutant shown. (B) Growth curves of fit1 mutants and wild-type littermates (c^ch +/c^ch +). The graph shows the mean weight of each group of mice (mutants or wild-type) plotted versus the day of weight measurement (the date of birth was designated day 0).