Drosophila melanogaster

Drosophila Melanogaster is a fruit fly species that belongs in the family Drosophiladae. It is commonly called the vinegar fly or common fruit fly.
They are only 2mm long, with a life cycle of approximately 2 weeks. Their genome has been sequenced in 2001; it has 165 Mbp that encode for 16000 Genes. There are 3 pairs of autosomal chromosomes, and one X and Y Sex chromosome.

It is an excellent Model organism that has been used for more than a hundred years for research due to its genetic advantages.

Drosophila are highly fecund, they can lay up to 100 eggs per day. They are small and easy to grow, with a short generation time. Mutant flies are readily available and they are easy to keep in large numbers. The mature larvae produce giant Polytene chromosomes with active genes.
Drosophila research has contributed in our understanding of many biological processes, like genetics, embryonic development and neurological diseases. 

Wildtype fruit flies are orange-brown with brick red eyes and black stripes across the abdomen.

There are some differences between male and females flies: males fruit flies are slightly smaller and darker in colour, because of a distinctive black patch on their abdomen. They also have sexcombs(a row of bristles on front leg) and spiky hairs around the reproductive organs. Females do not have sexcombs, or the black patch on their abdomen.

Evidence was found using Drosophila that mutagens like X-ray and chemicals increases the rate of mutation; discovered by Hermann Mullerin in 1927.  Mullerin used the CIB method that detects frequency in which large inversions (C) occur in the normal X chromosome of progeny from a female heterzygous fly. Mutation in the chromosome gives rise to a recessive lethal allele that means progenies with the certain genotype will not survive. The inversion affects the locus of the gene for eye type and the gene for eye type is sex-linked, so prescence of the lethal allele in the X chromosome means that any male who inherits the lethal allele or female that is homozygous for the recessive lethal allele will not survive.