![]() The Malpighian tubules excrete nitrogenous waste as uric acid, Drosophila gut epithelial morphogenesis genes which forms insoluble crystals, making the tubules opaque and hence visible in the mature embryo or larva. The four Malpighian tubules connect to the most anterior portion of the hindgut together they comprise an excretory organ analogous to vertebrate kidneys. The hindgut is the most posterior portion of the Drosophila gut (alimentary canal) and opens to the outside through the anus its primary function is water resorption. The mature hindgut and Malpighian tubules are single-layered, polarized epithelia a thin visceral mesoderm surrounds the hindgut, but not the Malpighian tubules (reviewed in 4). First, we review the development of these organs, and then describe the known genes that control this development. We describe here progress made toward understanding genes controlling epithelial morphogenesis, in particular the development of the posterior portion of the alimentary canal. In this way, one can, in an otherwise wild type organism, examine the effect of removing function of an essential gene in only a small group of cells (reviewed in 3).īecause of the multiple advantages of Drosophila genetics, investigators are using it to study molecules controlling various cellular processes. A number of techniques have been developed recently, based on transformation with P elements, that allow generation of clones of marked mutant cells. Furthermore, because it is a mobile element, an appropriately engineered P element can be used as a vector for genomic transformation, allowing a sequence of up to 20 kb to be inserted at random into the Drosophila genome 2. The small genome of Drosophila (1.5 × l0 8 base pairs, only one-twentieth the size of the mammalian genome) makes it relatively much easier to identify a sequence within a Drosophila than in a mammalian genomic library (reviewed in 1).Īnother crucial tool used in Drosophila molecular genetics is the mobile element P, which can be used as a mutagen (transposon tag), allowing the ready cloning of any gene mutated by insertion of a P element. With the advent of molecular techniques, the polytene chromosomes made it possible to map a particular cloned gene to a specific chromosomal position by using in situ hybridization, and conversely, to clone a gene by knowing its cytological location. Particularly significant, it possesses giant polytene chromosomes in the salivary glands of the larvae the detailed and reproducible banding pattern of these chromosomes allows the genetic map to be correlated with the cytological (physical) map. ![]() As research into this organism continued, other remarkable advantages emerged, namely that it possesses only four chromosomes (allowing each newly identified gene to be quickly mapped to a linkage group). ![]() At that time, the advantage of working with this small organism was that it reproduced rapidly in the laboratory, requiring only a simple growth medium, no special attention, and little expense. Work on Drosophila genetics began 90 years ago, when Thomas Hunt Morgan (who later received the Nobel Prize for his work) began studying inheritance in the fruit fly. ![]()
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