DROSOPHILA MELANOGASTER

Drosophila Melanogaster

Drosophila Melanogaster

Introduction

Drosophila melanogaster is a convenient organism for genetic study because it is small, breeds prolifically, and has a short generation time. Drosophila melanogaster has four chromosomes in each one of its cells. (1) When the genes are not passed on to the next generation in exactly the same form that is present in the parents then this can produce mutant forms of the organism.

(1) One type of mutation that has been discovered in Drosophila melanogaster is the ebony mutant. The phenotype of ebony flies includes a difference in body color, compared to the normal, which can vary from shining black to slightly darker than the normal.

(2) During the larva period the mutants can be identified by the darkened color of spiracle sheaths. (2) This mutation is recessive and the gene is located on chromosome.

(3) Looking at this information it can be determined that the ebony mutant is an autosomal recessive trait. The term autosomal means that the mutant gene is located on one of the three chromosomes besides the sex chromosomes. If the gene was located on the sex chromosome then the type of inheritance would be sex-linked. Recessive inheritance occurs when both matching genes must be abnormal to produce the recessive phenotype, compared to dominant inheritance, when only one copy of the abnormal gene is needed to produce the dominant phenotype.

(4) In recessive inheritance, when only one copy of the abnormal gene is present these individuals are known as carriers. Carriers have completely normal phenotypes.

(5) The following punnet squares will show the ratios of normal to mutant offspring following the autosomal recessive mode of inheritance. A=normal allele (dominant) a=mutant allele (recessive)

Geneticists have put a great deal of thought and effort into developing a uniform system of nomenclature applicable to Drosophila, plants (p&rticular1y maize), and mammals but, because of' the different situations (1) existing in the various organisms, these efforts have not been entirely successful. At present there is general acceptance of the main principles in regard to nomenclature. but minor differences exist among the systems of nomenclature and symbolism used in work with various organisms.

Drosophila melanogaster is a fruit fly, a little insect about 3mm long, of the kind that accumulates around spoiled fruit. It is also one of the most valuable of organisms in biological research, particularly in genetics and developmental biology. Drosophila has been used as a model organism for research for almost a century, and today, several thousand scientists are working on many different aspects of the fruit fly. Its importance for human health was recognized by the award of the Nobel prize in medicine/physiology to Ed Lewis, Christiana Nusslein-Volhard and Eric Wieschaus in 1995.

Mutant Trait of Drosophila Melanogaster

The mode of inheritance for the mutant trait giving a dark body phenotype was determined using Drosophila melanogaster. This phenotype was determined to be result of the ebony mutant trait. An initial mating was set up between homozygous mutant males, and homozygous normal virgin females. The F1 generation was examined and then allowed to self ...