Ii

Hox genes u

Hox proteins

Maintenance

Polycomb protein group

Trithorax group proteins

Figure 3.10

Hox genes are regulated by many inputs

Several classes of gene products regulate the initiation, modulation, and maintenance of Hox gene expression in the developing embryo and larva of Drosophila. Positive regulatory inputs are denoted by arrows; negative regulatory inputs are shown by a truncated line.

Ubx gene

Ubx regulatory elements

Ubx regulatory elements

Figure 3.11

The c/s-regulatory elements of the Ubx gene

(a) Three elements that regulate Ubx expression in the embryo are shown. Each element controls expression in selected subsets of parasegments.

(b) The BRE element contains binding sites for several segmentation proteins (Ftz, Hb, En, Tll) and a dorsoventral patterning protein (Twi) within a 500-bp span. (c) Expression driven by the BRE element in parasegments 6, 8, 10, and 12 is the net output of the various positive and negative regulatory inputs shown in this figure.

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