DROSOPHILA MELANOGASTER: CHARACTERISTICS, GENETICS, LIFE CYCLE - BIOLOGY - 2025

Drosophila melanogaster is a dipterous insect measuring about 3 mm and feeding on decaying fruits. It is also known as a fruit fly or vinegar fly. Its scientific name comes from Latin and means "lover of black-bellied dew."

This species is widely used in genetics because it presents a series of advantages that make it an ideal organism for this type of study. Among these characteristics are its ease of maintenance in culture, short life cycle, a reduced number of chromosomes, and presenting polygenic chromosomes.

Fruit fly Drosophila melanogaster. Taken and edited from: Sanjay Acharya

Other valuable characteristics of Drosophila melanogaster for genetic studies is that, due to the small number and size of its chromosomes, it is easy to study mutations processes in them. Additionally, more than half of the genes that code for diseases in humans have their equivalent detectable in this fly.

characteristics

Genetics and karyotype

The karyotype is the set of chromosomes that each cell of an individual presents, after the process in which the pairs of homologous chromosomes are joined during cell reproduction. This karyotype is characteristic for each particular species.

The Drosophila melanogaster karyotype is made up of one pair of sex chromosomes and three pairs of autosomal chromosomes. The latter are identified sequentially with the numbers 2-4. Chromosome 4 is much smaller in size than the rest of its peers.

Despite having a pair of sex chromosomes, sex determination in this species is controlled by the relationship between the X sex chromosome and the autosomes, and not by the Y chromosome as occurs in humans.

The genome, for its part, is the set of genes contained in these chromosomes, and in the fruit fly it is represented by about 15,000 genes made up of 165 million base pairs.

Nitrogen bases are part of the DNA and RNA of living beings. In DNA they form pairs, due to the double helix conformation of this compound, that is, a base of one helix pairs with a base in the other helix of the chain.

Mutations

A mutation can be defined as any change that occurs in the nucleotide sequence of DNA. Various types of mutations occur in Drosophila melanogaster, both silent and with obvious phenotypic expression. Some of the best known are:

Mutations in the wings

Wing development in Drosophila melanogaster is encoded by chromosome 2. Mutations in this chromosome can cause abnormal wing development, either in size (vestigial wings) or shape (curly or curved wings).

The first of these mutations is recessive, that is, for it to manifest itself phenotypically, the mutant gene must be inherited from the father and the mother simultaneously. In contrast, the mutant gene for curved wings is dominant, however, it only manifests itself when the carrier is heterozygous, since homozygotes are not viable.

The appearance of totally wingless organisms is also possible.

Mutations in the eyes

The eyes of the normal fruit fly are red. A mutation in the gene that codes for this color can cause it to work only partially or not at all.

When the mutation partially affects the gene, less than ordinary pigment is produced; in this case, the eyes acquire an orange coloration. On the contrary, if the gene does not work, the eyes will be completely white.

Another mutation occurs in the gene that encodes information for the development of the eyes. In this case, the flies will develop into adulthood, but without eyes.

Abnormal antenna development

Mutations in the gene that codes for antennae development can eventually cause a pair of head legs to develop instead of antennae.

Drosophila melanogaster. A mutation called antennapedia, where legs grow on the head instead of antennae. Taken and edited from: toony.

Mutations that affect body coloring

Pigment production and distribution in the body is controlled by different genes in Drosophila melanogaster. A mutation on the X sex chromosome can cause mutants to be unable to produce melanin, so their body will be yellow.

On the other hand, a mutation in the autosomal chromosome 3 can affect the distribution of the body pigment in this case, the pigment accumulates throughout the body, so it will be black.

References

1. M. Ashburner & TRF Wright (1978). The genetic and biology of Drosophila. Vol. 2a. Academic Press.
2. M. Ashburner, KG Golic & RS Hawley (2005). Drosophila: A laboratory Handbook 2nd edition. Cold Spring Harbor Laboratory Press.
3. Drosophila melanogaster. On Wikipedia. Recovered from en.wikipedia.org.
4. J. González (2002). Comparative evolution of chromosomal elements in the genus Drosophila. Doctor degree dissertation. Autonomous University of Barcelona, ​​Spain.
5. M. Schwentner, DJ Combosch, JP Nelson & G. Giribet (2017). A phylogenomic solution to the origin of insects by resolving crustacean-hexapod relationships. Current Biology.
6. S. Yamamoto, M. Jaiswal, W.-L. Chang, T. Gambin, E. Karaca… & HJ Bellen (2015). A Drosophila genetic resource of mutants to study mechanisms underlying human genetic diseases. Cell