author(s)
Dr. Sujit Kumar

abstract
The present investigations were made on the history and life cycle of Drosophila. Life-history traits or “fitness components” such as age and size at maturity, fecundity and fertility, age-specific rates of survival, and life span are the major phenotypic determinants of Darwinian fitness. Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called “fruit flies”. The entire genus, however, contains about 1,500 species and is very diverse in appearance, behavior, and breeding habitat. One species of Drosophila in particular D. melanogaster, has been heavily used in research in genetics and is a common model organism in developmental biology. Basic genetic mechanisms are shared by most organisms. Therefore, it is only necessary to study the genetic mechanisms of a few organisms in order to understand how the mechanisms work in many organisms, including humans. Drosophila melanogaster, the fruit fly a little insect about 3mm long, is an excellent organism to study genetic mechanisms. The general principles of gene transmission, linkage, sex determination, genetic interactions; molecular, biochemical and developmental genetics, chromosomal aberrations, penetrance and expressivity, and evolutionary change may all be admirably demonstrated by using the fruit fly Drosophila melanogaster. The life cycle of Drosophila is short and completes in about three weeks. Embryonic development, which follows fertilization and the formation of the zygote, occurs within the egg membrane. The egg produces larva, which eats and grows and at length becomes pupa. The pupa, in turn develops into an imago or adult. The duration of these stages varies with the temperature. Drosophila cultures ought to be kept in room temperature where the temperature does not range below 20 ^oC or above 25 ^oC. They are bred on fermenting medium which contains corn, dextrose, sugar and yeast extract. Their breeding ratio is 1:3 (male: female). The common culture contaminants include fungi, mites and bacteria. The male and the female are differentiated (under the microscope) based on their size, markings on their abdomen and presence of sex combs following anesthetization with ether.