Homebox genes in most segments prevent Distal-less gene expression. However in thoracic segments, limb formation is permitted through Distal-less gene expression. The original 3. Cluster forms at the intersection of Wingless and Dpp protein gradients. B. Determination of Disc Identity 1.
Differentiation is thought to caused by homeotic gene expression.
However, the specific molecules are still unknown. When the vestigial gene is added to other areas a wing grows in place of the normal structure. C. Determination of Disc Polarity 1. During first instar leg and wing imaginal discs require their anterior-posterior axis. The split between anterior and posterior compartments is defined by the expression of the engrailed gene in the posterior compartment.