Genes, Cell Division & Heredity — Extension · Life Science & Scientific Inquiry, Grade 7
Five focused units, a three-session investigation, chapter review, and chapter quiz.
Test a fictional inheritance probability model
Investigate
How do observed small samples compare with a Punnett model?
Materials
- Supplied genotype records
- Optional paper allele cards or two fair coins; notebook
Before you begin
Use fictional traits. No family trait survey, private genetic record, or biological breeding is needed. Paper symbols can replace all small counters.
Plan a fair test
Model Aa×Aa with equal independent gamete probabilities and complete dominance of A. Different rows are independent illustrative samples of twenty.
Method
- Build the Punnett square and expected genotype probabilities.
- Calculate expected counts for a sample of twenty.
- Compare all supplied groups and the pooled record with the expectation.
- Explain why a probability is not an exact small-sample schedule.
- State assumptions and propose a larger or independently repeated model trial.
Illustrative course data — use for analysis without equipment
Illustrative records: these are invented teaching data, not published measurements or the learner’s own observations. Actual measurements may differ; record them separately if you perform an optional suitable activity.
| Sample | AA | Aa | aa |
|---|---|---|---|
| A | 4 | 11 | 5 |
| B | 6 | 8 | 6 |
| C | 5 | 12 | 3 |
Analyze and explain
- What counts are expected out of twenty?
- How do pooled genotypes compare?
- Does sample variation alone disprove the model?
What a strong explanation includes
- Explain the relevant biological process accurately.
- Use the supplied evidence and show calculation steps with units where needed.
- Connect a labeled model or mechanism with the claim.
- State an assumption, evidence limitation, or useful next observation.
Parent / teacher guide: discuss after the investigation
Expected counts out of twenty are 5 AA, 10 Aa, and 5 aa. The pooled sixty contain 15 AA, 31 Aa, and 14 aa, compared with expected 15,30,15. Variation in finite samples is possible under the stipulated probability model and does not alone prove a different inheritance mechanism. The square is a fictional one-region model, not a calculator of complex personal traits. Examine independence and other assumptions before generalizing.
Compare this model with the learner’s actual evidence. Different measurements can support a different conclusion; check the reasoning and limitations, not matching wording.
Extend the chapter investigation by evaluating its evidence and proposing a better test.
Problem 1
Answer and explanation
Expected counts out of twenty are 5 AA, 10 Aa, and 5 aa. The pooled sixty contain 15 AA, 31 Aa, and 14 aa, compared with expected 15,30,15. Variation in finite samples is possible under the stipulated probability model and does not alone prove a different inheritance mechanism. The square is a fictional one-region model, not a calculator of complex personal traits. Examine independence and other assumptions before generalizing.
Problem 2
Answer and explanation
Expected counts out of twenty are 5 AA, 10 Aa, and 5 aa. The pooled sixty contain 15 AA, 31 Aa, and 14 aa, compared with expected 15,30,15. Variation in finite samples is possible under the stipulated probability model and does not alone prove a different inheritance mechanism. The square is a fictional one-region model, not a calculator of complex personal traits. Examine independence and other assumptions before generalizing.
Problem 3
Answer and explanation
Expected counts out of twenty are 5 AA, 10 Aa, and 5 aa. The pooled sixty contain 15 AA, 31 Aa, and 14 aa, compared with expected 15,30,15. Variation in finite samples is possible under the stipulated probability model and does not alone prove a different inheritance mechanism. The square is a fictional one-region model, not a calculator of complex personal traits. Examine independence and other assumptions before generalizing.