BySex Determination in Drosophila
Drosophila is a type of fly belonging to the family Drosophilidae. These flies are commonly referred to as “small fruit flies,” “pomace flies,” “vinegar flies,” or “wine flies,” as many species tend to hover around ripe or decaying fruits and vegetables.
The term Drosophila is derived from two Greek words: “δρόσος” (drósos), meaning “dew,” and “φιλία” (philía), meaning “love.” Thus, Drosophila translates to “dew lover.”
Drosophila flies serve as essential model organisms in genetic studies, including research on eye development, complex diseases, human disorders, genetic influences on behavior, chromosomal structures, mutations, and sex determination.
Sex Determination in Drosophila
| Common Name | Fruit Fly, Vinegar Fly |
|---|---|
| Scientific Classification |
|
| Chromosome Number | 8 (4 pairs: 3 autosomes + 1 sex chromosome pair) |
| Model Organism | Used in genetics, mutations, disease research, behavior studies |
| Sex Determination System | Sex Index Ratio (X/A Ratio) |
| Sex Determination Based on Ratio |
|
| Origin of Name | Greek: “δρόσος” (drósos) = Dew, “φιλία” (philía) = Love → “Dew Lover” |
| Significance in Genetics |
|
| Habitat | Common around ripe and decaying fruits, vegetables, and fermented substances |
| The Rajasthan Express: Sex Determination in Drosophila | |
Drosophila Chromosome Number and Its Role in Sex Determination
Drosophila possesses 8 chromosomes. In 1922,0 Calvin Bridges proposed the Genic Balance Theory to explain sex determination in Drosophila. According to this theory, sex determination is governed by the Sex Index Ratio, and the Y chromosome plays no role in the process.
Sex Index Ratio in Drosophila
The sex index ratio is determined based on the number of X chromosomes and the pairs of autosomal chromosomes (A).
Sex Index Ratio = Number of X Chromosomes / Pairs of Autosomal Chromosomes (A)
This ratio controls sex determination in Drosophila.
For Drosophila, the sex index ratio functions as follows:
- The ratio of X chromosomes to autosomes (X/A) determines the organism’s sex.
Specific Cases In Drosophila
- Sex Index Ratio = 1 → Results in a Female.
- Sex Index Ratio = 0.5 → Results in a Male.
- Sex Index Ratio between 0.5 and 1 (e.g., 0.6, 0.7, 0.8, 0.9) → Results in Intersex, which is Sterile.
- Sex Index Ratio > 1 (e.g., 2, 3, 4, 7, 8, etc.) → Results in Super Female / Meta Female.
- Sex Index Ratio < 0.5 (e.g., 0.4, 0.3, 0.2, 0.1, etc.) → Results in Super Male / Meta Male.
| Sex Determination Based on Sex Index Ratio in Drosophila | |
| Sex Index Ratio | Sex |
|---|---|
| 1 | Female |
| 0.5 | Male |
| 0.6, 0.7, 0.8, 0.9 | InterSex |
| Greater than 1 (2, 3, 4, 7, 8…) | Super Female / Meta Female |
| Less than 0.5 (0.4, 0.3, 0.2, 0.1…) | Super Male / Meta Male |
| The Rajasthan Express : Sex Determination in Drosophila | |
Note:
- If the sex index ratio is 0.5, the individual will be a normal male.
- If the ratio is less than 0.5, the individual will be a Super Male / Meta Male.
- If the sex index ratio is 1, the individual will be a normal female.
- If the ratio is greater than 1, the individual will be a Super Female / Meta Female.
- If the sex index ratio falls between 0.5 and 1, the individual will be intersex, which is sterile.
Learn how sex determination in Drosophila is regulated by the Sex Index Ratio (X/A Ratio). Understand chromosome numbers, genic balance theory, and key research findings in fruit fly genetics.
THE RAJASTHAN EXPRESS
