Fig. 6. Engrailed directly binds 1A4 fragment on polytene chromosomes. (A) In situ hybridization on polytene chromosomes. Localization of the transgene on 2L chromosome, in position 25C (shown by the arrow), using 1A4-GFP biotinylated DNA probe, detected by FITC anti-biotin antibody. Banding of the chromosome is shown by DAPI staining. (B1,B2,C1,C2) Immunodetection of Engrailed-binding sites on 2L polytene chromosome, in tramtrack heterozygous background [ttk804/+], identified by anti-Engrailed antibody (in red). (B1) Engrailed-binding sites of [1A4-GFP/+; ttk804/+] salivary glands. (B2) Same as B1 with DAPI staining. (C1) Engrailed-binding sites of [ttk804/+] salivary glands. (C2) Same as C1 with DAPI staining. The white arrow shows an additional Engrailed binding site at the insertion point of the transgene and the bracket indicates two sites close to it.