Figure 1.

Targeting construct to induce null mutations in Or43b. The Or43b gene was modified in vitro to introduce two stop mutations into the open reading frame. The first mutation (F→STOP) was introduced at codon 5, and the second (C→STOP) was introduced at codon 320, just before the DNA encoding the seventh transmembrane domain. A restriction site for the rare cutting restriction enzyme I-Sce1 was introduced into the Or43b gene between the two stop mutations. This construct was then cloned into the homologous recombination targeting P element vector pTV2 that contains the white eye color marker and FRT sites (Rong et al., 2002). Transgenic flies were created carrying the integrated construct on the third chromosome.