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Biology-Mr.Willets
Lab-Drosophila
Many genetics discoveries have been made by experimenting with the common fruit fly-
Drosophila melanogaster. Today, you will examine some flies that are living in their culture jars; some flies that have been killed and mounted on slides; and some living flies that I will anesthetize so that they can be examined more easily.
A. Get a culture jar and examine it. The top is made of porous material to let air in and out. The netting is there to make it easier for the flies to crawl around. Notice that the flies hang around the top. Turn the jar upside down to see if they move up. The blue material at the bottom is food. As the flies grow and reproduce, the food eventually gets used up and waste products accumulate. making the jar unsuitable for the flies and they die. Before that happens, flies can be moved to fresh culture jars.
Drosophila has four stages in its life. These can be seen in the culture jars. A description of each is on the back of this sheet. Read these descriptions and find each stage in the jar. The egg stage may not be easily seen. The larva stage is worm-like and will be crawling around in the food. The pupa stage is darker and usually attached to the side of the jar or to the netting
B. There are slides available at the front of the room. In the blue box are slides of male and female wild type flies (wild type is the name given to an organism with characteristics most commonly found in nature). Examine these using the stereoscopes. Identify males and females. Use the diagrams on the back of this sheet which show the differences between the sexes. The wild types have red eyes and normal wings.
In the green and white boxes are slides with flies having traits other than the wild type. One slide has flies with white eyes, one slide has flies with brown eyes and another has flies with sepia eyes (reddish-brown). Other slides have flies with dumpy wings or vestigial wings. Examine the pictures on the back for other wing types and eye shapes. Click Here for Fly Pictures
Make sure you examine all the different types of flies available. Each slide has a male and a female.
C. Female flies mate only once in their lives. When doing a genetics experiments with flies, you must be sure that the female has not already mated. Flies cannot mate until they are at least 10 hours old. To get virgin flies: 1) Remove and kill all flies from the jar (clear the jar) 2) Return in less than 10 hours. Any flies in the jar are less than 10 hours old and therefore have not mated. 3) Remove these virgin flies and separate males and females into separate jars 4) You now have separate jars of males and females that have not mated and cannot mate until you put them together the way you want.
D. I will have anesthetized some flies and placed them on paper pads. Come get these flies and a brush. The brush is used to move the flies around without hurting them. Examine the flies using the stereoscopes. Try to separate males from females. Use the diagrams on the back to help. When you are done, return the flies to the front of the room. Click Here For Fly Pictures
Questions-Answer these on a separate sheet. Use complete sentences. The information above and on the back will be helpful.
1) What are the four stages in the life of Drosophila?
2) Compare the markings on the abdomen of male and female flies.
3) Compare the shape of the abdomen of males and females.
4) What is the purpose of the two filaments on the Drosophila egg?
5) What structures develop during the pupa stage?
6) What name is given to the changes that occur during the pupa stage?
7) Before starting a particular cross, why must all the flies in the jar be removed and killed?
8) Many of the wing phenotypes shown on the back were created in labs by subjecting flies to mutation causing agents (mutagens). Why would many of these types of flies not be found in nature even if the mutations occurred naturally?
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