P{lacW} transposon insertions with gradual expression of reporter genes

In Drosophila, insertions of the P{lacW} transposon led to uncommon express ion patterns of the reporter genes white and lacZ: gene activity was gradua lly reduced in the neighboring cells along the dorsal-ventral or proximal-d istal axes. Using in situ hybridization, the gradual gene expression was sh own to be caused by P{lacW} insertions in regions 40A (lines G1 and G2) and 69C (line G3) of the Drosophila genome. The expression patterns of genes l acZ and white were similar in eye cells of each line. In salivary gland pol ytene cells of G3 flies, the lacZ expression was also gradually reduced, wh ich indicates the existence of a mechanism maintaining the gene activity gr adient endomitoses.