In History, we had used several organisms as a model for clinical trials and most effectively for Genetic research. Certain organism’s genetic arrangements are more or less similar to some species. As a result, early day biologists used highly complex organisms like horses, donkeys, etc., even when their research is at a baby stage, resulting in numerous reported death of such animals. Most of the time, the number of births given by such animals in their lifetime can be counted on our ten fingers. Hence large-scale usage of these animals as models could lead to the endangerment of their species.
So the ethical committee and social activists demanded some restrictions on such trial organisms. They drafted few criteria for such biological research, in order to prevent animals like these from moving towards endangerment or the worst case, extinction. Here as follows are some major criteria a model organism should have habilitated,
- It needs to have a comparatively short life span (for quick observation)
- It should attain its maturity quickly (to analyse its metabolic development)
- It should be capable of producing a large number of offsprings (for conserving its species and continuous experimental purpose).
So the scientists had to replace the organisms like horses, guinea pigs, monkeys,etc., that were used as a model, with small, short life spanned and multiple offspring producing organisms such as Common Fruit fly (Drosophila melanogaster), Roundworm (C.elegans), Zebrafish and African Clawed Frog (Xenopus). Of these, we are about to see a small model organism that we can find in our day-to-day life, with only 4 chromosomes. It is Drosophila melanogaster (Common fruit fly).
Drosophila has been a versatile model organism for a century. In 1901, this efficient research was started by William.E.Castle, C.W.Woodworth at Harvard University and followingly the team included Thomas Hunt Morgan.
In 1907, Thomas Hunt Morgan tend to breed the Drosophila extensively for the experiments of mutation and to prove the theory of inheritance proposed by Gregor Johan Mendel. Theory of Inheritance states that heredity is the result of discrete units of inheritance, and every single unit (or gene) was independent in its actions in an individual’s genome (Before his declarations, DNA was considered to be the only genetic material). Now let’s come back to the concept of mutation. It is a sudden alteration of the normal DNA sequence that later causes abnormal reactions or expressions in the organism’s body.
Thomas Hunt Morgan mutated the Drosophila by several means. In 1909 he had observed some smaller mutation patterns which were proving Mendel’s theory of inheritance. In the year of 1910, he got a mutant which was a white-eyed male fly (normally common fruit fly’s eyes were brick red coloured). This was the first success in using Drosophila melanogaster as a model organism.
Why Drosophila?
60% of its genome is homologous (i.e. similar) to the human genome. Approximately, 75% genome homologs with human genetic diseases and some cancers. As a result, it emerges as a valuable mode of drug discovery and clinical model organism in the cheapest mode. These fruit flies are used to evaluate the effects of novel drugs on the biochemical pathways. This allows an alternate way and faster results than using cell culture and mammalian organisms which have more complex biology and are also more expensive to maintain. It is more cost-effective and time-efficient to screen them for compounds while testing the effect of drugs, in comparison with mammalian models. Also, we can find the drug efficacy by injecting them with a lower dose of drugs that we intend to use on humans, due to our homologous genome. In Drosophila it is easy to manipulate the genetic background because of its shorter life span of 10 days on room temperature(25°C) and its productivity.
Am not I
William Blake
A fly like thee?
Or art not thou
A man like me?
This poem named ‘The Fly’ by William Blake compares man with a fly in several aspects. Published in 1794, he would have been surprised to know the significance of flies for humans, if he was alive till now. To date, 6 Nobel Prizes have been awarded for the research on Drosophila.
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