OBSERVATIONS OF DROSOPHILA EGGS
Name: _________________________________
Remember to maintain your laboratory notebook entries as you conduct the laboratory activities.
Otherwise, you need to do so on your own time, and before your notebook is due.
Grape Juice Agar Method
1. Anesthetize the flies in your grape juice agar egg laying apparatus by placing the mesh side
down on the flow buddy fly pad. Determine their gender and count each. Record the eye
color and numbers in the table below and return these flies to an appropriate labeled vial of
fruit flies.
2. Observed each of the prepared quadrants and tally the number of eggs in each.
Agar
Agar +
Scoring
Agar +
Yeast
Agar +
Scoring and
Yeast
Eye
Color &
Number
of Adult
Males
Eye
Color &
Number
of Adult
Females
Number of
Fruit Fly
eggs
3. Record your data on the white board and copy everyone’s data into your laboratory
notebook. Make specific observations regarding the egg laying, calculate and prepare a
graph for your results, describe your graph in words, and make conclusions regarding egg
laying in drosophila.
Grape Juice Agar Eggs
1. After you have completed all the work above, prepare a clean petri dish by just filling the
bottom surface with insect Ringer’s solution (a salt solution). Then, using a needle or similar
implement transfer 5 eggs to the Petri dish. Observe the eggs under a dissecting
microscope. Sketch the eggs, and record specific observations. If you have yet to determine
the names of the egg parts, do so, label your drawing, and determine their specific functions
as well.
2. Then, transfer one or more (but not all) of your eggs in a single drop of Ringer’s solution to a
glass slide and observe it using a compound light microscope*. Place a small drop of
Toluidine blue stain over the eggs. This stain will not fix or kill the specimen. Observe the
eggs and record additional information about its structure in your laboratory notebook.
3. Transfer a separate individual egg onto another slide. Place a drop of undiluted Chlorox
solution onto the egg and let stand for 5 minutes. This should dechorionate the egg. Wick
away the Clorox and rinse the egg by applying a new drop of Ringer’s solution. You may
need to do this a couple times to remove the Chlorox. Observe the egg using a compound
light microscope, and attempt to determine its stage of the development using the pictorial
reference provided.
*Tips on Using a Compound Light Microscope
1. Solve your own problems by reading the directions carefully.
2. Plug in the microscope. Clean the lenses with lens paper to remove any smudges that may
distort the image of your specimen.
3. Turn on the light and look to see that a beam is shining through the circular hole in the stage.
If it isn’t you will notice an adjustable dimer that can be maneuvered to change the amount of
light shining through the stage on the lower left hand side of the microscope. If you have a
specimen already prepared on a slide it is also important that you can see that light is passing
through the specimen.
4. Turn the rotating objective lenses so that the lower power (red), or shortest, lens is in line
above the stage. The low power objective along with the eye piece magnifies the specimen
100X. You will also want to adjust the ring below the stage so that the line is lined up with the
appropriate power.
5. Use the coarse adjustment knob (large inner knob) to move the stage as far away from the
objective lenses as possible.
6. Place the slide on the stage by pull back the slide lever, slide the slide in place at the back of
the slide holder, and carefully bring the lever back in place so that it holds the slide firmly.
7. Finally, peer through the eye piece and use the coarse adjustment knob to slowly bring the
stage closer and closer to the low power objective lens. If you your specimen is under a cover
slip, it can sometimes help to focus on the edge of the cover slip before using the slide controls
to move the specimen into place.
8. Once you have focused on the specimen using the coarse adjustment knob, you can further
use the fine adjustment knob (smaller outer knob) to more carefully control the focus.
9. If your specimen is small enough that higher magnification would be appropriate, carefully
rotate to the medium power objective, the next largest lens in length, is positioned in line over
the specimen. You shouldn’t need to adjust the coarse adjustment. As you increase in
magnification, the amount of light shining through the specimen is reduce, and may need to be
adjusted. This medium power objective along with the eye piece magnifies the specimen
400X. Again, you will also want to adjust the ring below the stage to the appropriate power.
10. You may use the next higher magnification is necessary, with similar caveats as mentioned for
the medium power lens. The high power objective along with the eye piece magnifies the
specimen 1000X. Adjust the ring under the stage again.
11. DO NOT rotate the objectives to the oil emersion lens, without being instructed on how and
when to do so. This lens requires supplementary materials for its use. If it is used improperly,
it can damage the lens.
12. When finished, 1) return or dispose of the slide in an appropriate manner, 2) return the
objectives to their original low power position, 3) replace the cord appropriately, 4) replace the
microscope cover, and 5) return the microscope to the microscope cabinet.