Drosophila melanogaster

Within a few years of the rediscovery of Mendel's rules in 1900, Drosophila melanogaster (the so-called fruit fly) became a favorite "model" organism for genetics research.

• The flies are small and easily reared in the laboratory.
• They have a short life cycle The figure shows the various stages of the life cycle (not all drawn to the same scale). A new generation of adult flies can be produced every two weeks.
• They are fecund; a female may lay hundreds of fertilized eggs during her brief life span. The resulting large populations make statistical analysis easy and reliable.
• The giant ("polytene") chromosomes in the salivary (and other) glands of the mature larvae.
  • These chromosomes show far more structural detail than do normal chromosomes, and
  • they are present during interphase when chromosomes are normally invisible.

• Its embryo grows outside the body and can easily be studied at every stage of development.
• The blastoderm stage of the embryo is a syncytium (thousands of nuclei unconfined by cells) so that, for example, macromolecules like DNA injected into the embryo have easy access to all the nuclei.
• The genome is relatively small for an animal (less than a tenth that of humans and mice). [View]
• Mutations can targeted to specific genes. [Link to discussion of transposons.]

• In embryonic development:
  • How a single fertilized egg can give rise to different kinds of cells.
  • How transcription factors guide the organization of the body plan of the embryo.
  • Signals needed to guide the development of the central nervous system.
  • Genetic controls over the building of
    • wings
    • legs
    • eyes
• How the giant chromosomes reveal changing patterns of gene expression.
• Forces at work in evolution
  • sexual selection
  • the benefits of sexual reproduction
• Genetic control of
  • circadian rhythms.
  • foraging behavior