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Resveratrol is produced by a range of plants in response to environmental stress and appears to work by activating a key gene in mammals called SIRT1 which produces an enzyme linked to extending lifespan . These events resulted in numerous gene families having orthologous genes on separate chromosomal segments , or paralogons , in humans and other mammals . The inert sequences may disrupt a key gene , for example , and uncontrolled replication may ensue-the beginning of cancer . Based on the developmental genetics of wing formation in Drosophila and comparisons of homeotic gene expression and function between insects , it appears that forewing patterns evolve independently of homeotic genes , whereas hindwing patterns are Ubx-regulated modifications of the respective forewing patterns . It has even been proposed that it could be the homeotic gene corresponding to this part of the anterior to posterior axis . Drosophila homeotic gene abdominal-A is important for developpemental decisions in the anterior abdomen . Since cultured brain cells can be induced to divide with applied growth factor , we hypothesized that an in vivo application of growth factor , if able to induce cell division , could enhance MLV-based gene transfer to the adult brain . The apterous gene is expressed ( solid block ) in a dorsal respiratory lobe , whereas the Distal-less gene is expressed ( edges ) in the other limb branches.54 An ancestor-descendent relationship between the limbs in the box is not implied .