Genome
The genome of D. melanogaster (sequenced in 2000, and curated at the FlyBase database) contains four pairs of chromosomes: an X/Y pair, and three autosomes labeled 2, 3, and 4. The fourth chromosome is so tiny that it is often ignored, aside from its important eyeless gene. The D. melanogaster sequenced genome of 139.5 million base pairs has been annotated and contains approximately 15,016 genes. More than 60% of the genome appears to be functional non-protein-coding DNA involved in gene expression control. Determination of sex in Drosophila occurs by the ratio of X chromosomes to autosomes, not because of the presence of a Y chromosome as in human sex determination. Although the Y chromosome is entirely heterochromatic, it contains at least 16 genes, many of which are thought to have male-related functions.
Read more about this topic: Drosophila Melanogaster