Alice Wang

Genetics of Organisms

Question: Is an unknown Drosophila mutation dominant or recessive, and is it X-linked or autosomal?

Hypothesis: The offspring of a pair of reciprocal Drosophila crosses is determined by which the mutation is dominant or recessive and whether it is x-linked or autosomal.

Materials:

  • Drosophila cultures
  • Dry active yeast
  • Fly nap wands
  • Ether
  • Fruit fly media
  • Small paint brushes
  • Dissecting microscopes
  • Glass vials
  • Foam stoppers

Outline:

  1. First week: Immobilize and remove the adult flies of the original vial. Observe them carefully under the dissecting microscope. Separate the males from the females and look for the mutation(s). Note whether the mutation(s) is/are associated with the males or females.
  2. Place the parents in the morgue( jar containing alcohol). Label the vial containing the eggs or larvae with the symbols for the mating. Also label the vial with your name and date. Place the vial in a warm location.
  3. Second week: Begin by observing the F1 flies. Immobilize and examine all the flies. Record their sex and characteristics. Consider the conclusion s that can be drawn from these data. Place five or six pairs of F1 flies in a fresh culture bottle and the rest of the flies in the morgue.
  4. Third week: Remove the F1 flies from the vials and place them into the morgue. The F2 generation are the eggs and /or larvae in the vial. Place the vial in a warm place.
  5.  Fourth week: Begin removing the F2 flies. Record their sex and the presence or absence of mutation(s). The more F2 flies collected, the more reliable the data will be.

Procedure:

Step 1: Preparing Culture Tubes

1. Obtain a clean culture tube.

2. Place approximately one inch of culture media into the tube.

3. Add an equal amount of water

4. Sprinkle in about 8 grains of dry active yeast.

5. Place foam stopper on the top of vial.

6. Label the vial with the proper generation and cross

Step 2: Anesthetization of flies by using “Fly Nap”

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1. Obtain a vial of flies.

2. Gently tap the vial to knock flies away from the top of the foam stopper.

3. Soak the wand with fly nap solution and gently place it in the vial

5. After the flies stop moving, gently, tap the vial of flies onto a piece of paper

Step 3: Sexing and Counting Flies

1. Turn on the top light. Make sure the bottom light is OFF.

2. Using the small paint brush, sex and sort the flies on to different halves of a piece of paper

3. Male flies have sex ...

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