Fig. 3. Analysis of crossregulation between squint and cyclops. Time course of sqt expression in wild-type (A-E), sqt mutant (J) and cyc mutant embryos (F-I). cyc expression in wild-type (K-O), sqt^-/-; cyc^+/+ (P-S) and sqt^-/-; cyc^+/- (T-V) embryos. Developmental stages are indicated at the bottom, except for E and J, which are 5 h embryos as noted in the panels. Although the absence of sqt transcripts in sqt mutants is consistent with an autoregulatory role for sqt, it is also possible that the 1.9 kb insertion in the sqt^cz35 allele affects the stability of the message. Animal pole views are shown for all embryos prior to 6 h, and dorsal views are shown for embryos at 6 and 8 h, except for the lateral images in D,I. The genotypes of all embryos shown were determined by PCR after photography, except for E and J, for which the genotypes were inferred from the phenotypic ratio evident in progeny from a sqt/+ intercross (10 mutants/33 progeny).