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Genetic Experiment Design Worksheet

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Genetic Experiment Design Worksheet

You are investigating how an inherited trait might appear in offspring. Use a safe paper-and-coin simulation—not real people or animals. In this model, B represents a dominant allele for purple petals and b represents a recessive allele for white petals. The two parent plants are Bb and Bb. For each simulated offspring, flip one coin for each parent: heads passes B and tails passes b. Record the resulting genotype and predict the petal color. Real inheritance is more complex; this simplified model is for practicing experimental design and probability.

Plan the investigation

Use the model description above to answer Questions 1–4.

1.Choose the best research question for this simulation.

How does the offspring’s genotype relate to its predicted petal color when two Bb parents are crossed?
Which petal color looks prettiest?
Do coins cause plants to change their genes?
Which parent is more important?

2.Write a testable prediction for the proportion of purple-petaled and white-petaled offspring in a large set of trials.

3.Match each part of the investigation to its role: number of offspring trials; predicted petal color; parent genotypes; coin-flip outcomes.

Independent variable (the factor deliberately changed)
Dependent variable (the result recorded)
Conditions kept the same
Random process used to model allele inheritance

Parent genotypes
Number of offspring trials
Predicted petal color
Coin-flip outcomes

4.Put these procedure steps in a sensible order by writing 1–4: record the offspring genotype and predicted color; set up one coin for each parent; flip once for each parent; repeat for the planned number of offspring.

Predict, collect, and interpret

Use the model cross Bb × Bb and the sample results below. Each row represents 20 simulated offspring.

B (Parent 2)

b (Parent 2)

B (Parent 1)

___

b (Parent 1)

___

5.Complete the Punnett square above. What fraction of the four possible genotype combinations is bb?

Run

Purple-petaled

White-petaled

6.Across all three runs, how many offspring were recorded, and how many were white-petaled?

7.What percentage of the sample results were white-petaled? Show or describe how you worked it out.

8.True or false: If a trait is dominant, it must appear in every offspring. Explain your choice using the Bb × Bb model.

9.The sample result is 25% white-petaled. Does this prove that exactly 25% of all offspring from these parents will be white-petaled? Explain why or why not.

10.Choose the fairest way to improve the investigation’s reliability.

Run more trials while keeping the parent genotypes and coin-flip method the same.
Change the parent genotypes each time and combine all results.
Stop as soon as the results match the prediction.
Count only the purple-petaled outcomes.

11.Give one conclusion supported by the sample data and one limitation of this paper-and-coin model.