Identification of Various Mutant Types of Drosophila ( Practical)

 

Identification of Various Mutant Types of Drosophila 

Aim

To study and identify different mutant types of Drosophila melanogaster using live cultures or photomicrographs.

Background

Drosophila melanogaster (fruit fly) is one of the most widely used model organisms in genetics. Many visible mutants exist that differ from the wild type in traits such as eye colour, wing shape, body colour, and bristle pattern. By observing and comparing these mutants with the wild type, students learn about inheritance, mutation, and phenotypic variation.

Materials Required

1. Culture vials of Drosophila (wild type and mutant strains) OR photomicrographs

2. Stereomicroscope/dissecting microscope

3. Fine camel hair brush or forceps

4. Ether or CO₂ anesthetizer for immobilizing flies

5. White observation plate/paper

6. Reference chart of common mutants

Procedure

1. Immobilization: Anesthetize the flies using ether or CO₂ and transfer them gently to a white plate.

2. Observation setup: Place the flies under a stereomicroscope for detailed examination.

3. Wild type identification: First, observe wild type flies (red eyes, long wings, brownish-yellow body, normal bristles).

4. Mutant screening: Compare each fly with wild type and note deviations.

5. Classification: Group mutants into categories: eye colour mutants, wing mutants, body colour mutants, and bristle mutants.

6. Recording: Enter your observations in a tabular form with trait, wild type state, and mutant phenotype.

7. Photomicrograph study: If using prepared images, carefully identify visible differences and record them.

Photomicrograph of Mutant Drosophila

Observation Table

Trait Category	Wild Type	Mutant Example	Mutant Description
Eye colour	Red	White, sepia, brown	Altered/loss of eye pigment
Wing shape	Long, flat	Vestigial, curly, dumpy	Reduced or abnormal wings
Body colour	Brownish-yellow	Ebony (black), yellow	Pigmentation altered
Bristle pattern	Normal	Forked, singed, stubble	Abnormal bristle form

 

Common Mutants in Drosophila

1. White eye – complete loss of eye pigment

2. Sepia eye – dark brown eyes

3. Vestigial wing – small, shriveled wings

4. Curly wing – wings curved upwards

5. Ebony body – black body colour

6. Yellow body – pale yellow cuticle

7. Singed bristles – bent or twisted bristles

Precautions

1) Do not over-anesthetize flies as they may die.

2) Handle gently with a brush to avoid damaging wings or bristles.

3) Always compare with wild type before recording a mutant phenotype.

4) Keep cultures healthy for repeated use.

Viva Questions

1. Why is Drosophila melanogaster a model organism in genetics?

2. Define wild type and mutant.

3. Give two examples of eye colour mutants.

4. What is the phenotype of vestigial wing mutant?

5. Why is identifying mutants important in genetic studies?

FAQs

Q1. Can photomicrographs replace live cultures?

Yes, they are commonly used where live cultures are unavailable.

Q2. How many mutants are generally studied in one practical session?

Usually 4–6 mutants along with wild type.

Q3. Are these mutations natural?

Yes, most originated spontaneously and are maintained as laboratory stocks.

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