Drosophila melanogaster


 

PURPOSE 

The main purpose of this laboratory hour was to discern according to physical differences the Drosophila melanogaster in males and females, to enhance our observational skills in discerning wild type Drosophila from the mutant phenotype and to gain a better understanding of the mutations in different types of Drosophila and how can be visually distinguished.  

INTRODUCTION 

Drosophila melanogaster is a 2.5 mm, red-eyed, yellow-brown colored fly that habitats the fruits. It lives 30 days. Drosophila`s gender is arranged by the X to A ratio. It demonstrates dimorphism, where females differ from males because they are bigger, have a pointy and lighter  posterior instead of a round one and their forelegs don`t have sex comb [1]. 

The reasons that have made Drosophila so ubiquitously used are: 

  • Drosophila is easy accessible. 
  • It produces lots of offspring in a short period of time. 
  • It has a short genome of 15,016 genes and only 4 pairs of chromosomes, X/Y pair and 3 other chromosomes where the 4 one has a minute size. Y chromosome helps in establishing male characteristics in the male flies.  
  • It is easily manageable in the conditions of laboratory. 
  • Males and females are easily discerned from each other and virgin species are easily distinguished. 
  • Lots of techniques to manipulate it have been developed.  
  • In its salivary glands the polytenechromosomes, where transcription and genetic activity occur, are easily observed. 
  • 75% of the illnesses occuring on that fly have equivalent in the humans. 
  • 50% of its protein sequences have equivalent ones in different mammals. 
  • Beneficial about studying the activity of the chromosomes that stabilize recessive lethal gene`s activity [2]. 

Drosophila melanogaster shows ectothermicity and its habitat`s temperature affects the reproduction, where 290 c is the ideal temperature. The females which produce on average 50-75 eggs on the day and they develop after one day on small white larvae. In 7 days they become ready for pupation, that lasts 2 days and adult flies arise [3].  

Drosophila is manipulated for the study of genetic illnesses, such as: Parkinson, Alzheimer, Huntigton`s disease and other biological phenomena, such as oxidative stress, cancer, diabetes, obesity, ataxia and the process of aging [4]. 

The genetic markers on the Drosophila, such as inserts of P elements are advantageous in studying Drosophila `s different mutants, such as 

  • Cy1 (curve)-  It differs from the wild type as its wings are curved always from the body.  
  • e1 (ebony)- It is black in all its parts of the body, and the heterozygotes too develop blacker    color than wild types.    
  • Sb1 (Stubble): its bristles are thick and short compared to the wild one. 
  • w1 (White): Its eyes look white.  
  • y1  (Yellow): It is thoroghly colored in yellow [5].  

 

MATERIALS & METHODS 

Firstly the flask containing the Drosophila-s was taken and the bottle was knocked up on the bench in order to have the flies in the bottom part of the breeding flask. An empty flask was taken and positioned over the first chamber after its plug was removed. Benefitting from the negative geotropism of the Drosophila melanogaster move up toward the top of the new flask.  In the moment flies position in the top part of the new flask, the first breeding flask is removed and a plug that contains a piece of cotton with ether is placed over the first one. After the motion of flies stopped, the plug that contained ether was immediately taken off the flask in order to protect the flies from possible death or sterilization that occurs by over-exposure to ether. The flies were positioned in a petri dish and observed under stereomicroscope, by using a soft brush to change the flies` s position and obtain proper images of the flies. The same procedure was repeated three times as there were three flasks of Drosophila melanogaster.  

 DISCUSSION  

During the observations with stereomicroscopes, different types of Drosophila melanogaster were seen under microscope. The larvae and pupae were observed too. Presence of larvae could be distinguished, because of the physical characteristics that distinguish them, such as its white color and an undifferentiated form. Also the presence of pupae could be distinguished, because of the brown color over it and the undifferentiated form. In the samples we observed, there was one vestigial wing Drosophila melanogaster, but it was dead. The other types of Drosophila could be observed. The female wild type could be distinguished, because of its red eyes, posterior end and its light brown color over its abdomen. On the other hand, the male Drosophila melanogaster could be observed under the microscope due to its physical characteristics: dark brown colored and round abdomen. The white eyed mutant type could be observed, due to the presence of the white eyes on them. The females and the males in the white eyed mutant type could be distinguished due to the abdomen `s color and shape. Also the yellow mutant type could be observed too, distinguished from its color over Drosophila`s body. 

 

REFERENCES 

  1.  http://flybase.org/ retrieved 02.12.2015 from 
  1. http://animaldiversity.org/accounts/Drosophila_melanogaster/ retrieved 02.12.2015 from 
  1. http://www.d.umn.edu/~pschoff/documents/08Drosophila.pdf retrieved  02.12.2015 from 
  1. http://www.nig.ac.jp/labs/EvoGen/pdf/akashi_genetics94.pdf retrieved  02.12.2015 from 
  1. http://www.genetics.org/content/76/4/755.full.pdf retrieved 02.12.2015 from 

 

 

 

 

 

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