Worksheet

Fruit Fly Strains: When a Gene Changes

Grade 8 practice with gene mutations: read fruit fly lab data and decide when a changed protein is harmful, helpful or neutral.

Grade 8ScienceInteractive · Printable

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1 NGSS standard
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10 questions
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Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Matching, Sorting, Short answer

About this worksheet

What students practice

Students explain how a change in a gene can change a protein and a trait.
Students use survival data to decide if a mutation is harmful, helpful or neutral in an environment.

How to use

Read the lab description aloud and trace the gene, protein and trait chain for one strain together before students analyze the table on their own.

Curriculum

NGSS standard covered

MS-LS3-1

Explain how gene mutations can change proteins and have harmful, helpful or neutral effects on an organism.

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Fruit Fly Strains: When a Gene Changes

Use lab data to explain how mutations change proteins and traits.

Part 1: Five strains of flies

Read the passage and the data table, then answer the questions.

A Summer in the Fly Lab

1Rohan Bergstrom spent his summer helping in Dr. Ifeoma Bassey's genetics lab at the community college. The lab raises fruit flies in plastic vials with a layer of food at the bottom. Fruit flies are useful for studying genes because they are small, easy to feed and produce a new generation in about two weeks.

2Dr. Bassey explained that a gene is a section of DNA that carries the instructions for building a protein. Proteins do much of the work in a body: some give color, some build structures such as wings and some break down chemicals. A mutation is a change in the DNA of a gene. Because a protein's shape decides what it can do, a mutation that changes the protein's shape can change how well that protein works.

3The lab keeps five strains of flies. Each mutant strain differs from the normal strain by one known mutation. In strain W, the eye-color gene is changed and the red pigment protein is not made. In strain V, the wing gene is changed and the wing protein is misshapen. In strain N, a gene is changed, but tests show the protein it builds has the same shape as the normal protein. In strain R, the gene for a protein that breaks down a pesticide is changed, and the protein works faster than normal.

4Rohan ran two tests with 100 adult flies from each strain. In the pesticide test, flies spent 24 hours in a cage with a low dose of pesticide, and he counted the survivors. In the shelf test, flies were released at the bottom of a tall clear box with food on a high shelf, and he counted how many reached the food within one hour. Dr. Bassey told him that differences of 3 percentage points or less are within the normal spread between repeated trials, so they do not count as a real difference.

5In ordinary vials, with food at the bottom and no pesticide, flies of all five strains lived about the same length of time, roughly 40 to 50 days. Rohan recorded each test result in the table below. He also noted that the lab keeps every strain in its own labeled vials, so flies from different strains do not mate and mix their mutations.

Rohan's results (100 flies per strain in each test)
Strain	Visible trait	Pesticide survival (%)	Reached shelf food (%)
Normal	Red eyes, full wings	30	88
W	White eyes	29	79
V	Small crumpled wings	29	12
N	Looks normal	31	87
R	Looks normal	86	89

Which order shows how a mutation leads to a changed trait in these flies?

A. Changed protein → changed DNA → changed trait
B. Changed trait → changed protein → changed DNA
C. Changed DNA → changed trait → changed protein
D. Changed DNA → changed protein → changed trait

Use the table.

How many more percentage points of strain R flies than normal flies survived the pesticide test? percentage points

Use the table.

In the shelf test, how many percentage points lower was strain V than the normal strain? percentage points

Which strain's mutation seems to be neutral in both tests?

A. Strain V
B. Strain N
C. Strain W
D. Strain R

Match each protein change to the trait it causes in these strains.

The wing protein is misshapen.
The red pigment protein is not made.
The pesticide-breaking protein works faster.
The protein keeps its normal shape.

A. The fly has small, crumpled wings.
B. The fly has white eyes.
C. The fly shows no visible difference.
D. The fly survives pesticide better.

Why does N look normal even though its gene has a mutation?

A. Its protein kept the same shape, so the protein still does the same job.
B. The flies grew out of the mutation as they became adults.
C. The mutation was fixed when the flies were moved to a new vial.
D. Its mutation is in a gene that builds no protein in fruit flies.

Part 2: Harmful, helpful or neutral?

Use the passage and the table. Remember that a difference of 3 percentage points or less does not count.

Sort each strain and setting by the effect of its mutation compared with normal flies.

Strain R in the pesticide testStrain V in the shelf testStrain R in the shelf testStrain W in the shelf testStrain V in the pesticide test

Harmful	Helpful	Neutral

Rohan says the strain V mutation is harmful to a fly wherever it lives. Which evidence from the page best challenges his claim?

A. Strain V has a misshapen wing protein, so its wings are small and crumpled.
B. Strain V reached the shelf food 76 percentage points less often than normal flies did.
C. In ordinary vials with food at the bottom, strain V lived about as long as normal flies.
D. In ordinary vials, strain V flies died about 20 days sooner than normal flies.

A farm field near the college is sprayed with the same pesticide each summer. Wild fruit flies there sometimes carry the strain R mutation. What would you predict?

A. Flies with the mutation would be more likely to survive the spraying than other flies.
B. Flies without the mutation would change their genes after their first spraying.
C. Both kinds of flies would survive at the same rate, as they did in the shelf test.
D. Flies with the mutation would tend to die sooner, because mutations are usually bad.

10.

Can the same mutation be helpful in one setting and neutral in another? Use strain R to write a claim, give evidence from the table and explain your reasoning with the ideas of genes, proteins and traits.