DNA, Inheritance & Gene Expression — Investigation · Life Science: Biology, Grade 10
Use DNA and inheritance models while testing their limits with expression and variation evidence.
Compare Expected and Observed Inheritance
Investigate
How close must a small sample be to a probability prediction?
Use three sessions: define question, boundary, model and route; collect or analyze the supplied repeated records; then graph, explain, revise and submit the notebook. Home-study activities do not certify NYSED laboratory minutes or mandated investigations.
Materials
- Two coins or cards representing A/a gametes
- Notebook
- Calculator
- Supplied sample counts
Before you begin
Use the supplied paper-and-data model. This activity requires no biological samples, cultures, personal health information, or tests on people.
Plan a fair test
Model Aa × Aa with independent, equally likely gametes and complete dominance. Repeat the same rule; do not force each group of four outcomes to include every possible combination.
Method
- Write expected AA, Aa, and aa probabilities before generating data.
- Draw or toss one allele for each parent, record the offspring, then return cards or reuse coins.
- Generate at least 20 model offspring, or analyze the supplied groups.
- Compare observed proportions with expectations and keep sample size visible.
- Combine the supplied samples and compare the combined proportion with each small sample.
- Explain why a mismatch alone does not decide whether the model is valid; propose more evidence.
Open the investigation data (illustrative)
Illustrative data authored for this activity, not an actual experiment or an official mandated investigation. Use them as supplied evidence, not as your own observations.
| Sample | AA | Aa | aa | Total |
|---|---|---|---|---|
| Group 1 | 6 | 11 | 3 | 20 |
| Group 2 | 4 | 9 | 7 | 20 |
| Group 3 | 5 | 10 | 5 | 20 |
Analyze and explain
- What recessive percentage occurs in each group and the combined sample?
- Does the model guarantee exactly five aa in every twenty?
- Why should this model not be labeled a prediction of actual human eye color?
- Separate collected measurements from the supplied illustrative records.
- Explain how labeled mechanisms constrain the pattern rather than only restate the graph.
- Propose a further comparison that could distinguish an alternative explanation.
What a strong explanation includes
- Shows expected genotype and phenotype probabilities
- Calculates observed percentages with correct denominators
- Explains sampling variability and independence
- Names the limits of a one-gene model
- State units, boundary, comparable conditions and model assumptions.
- Retain a first explanation and an evidence-supported revision.
Parent / teacher guide: discuss after the investigation
Expected aa frequency is 25%. Group percentages are 15%, 35%, and 25%; combined, 15 of 60 = 25%. The agreement in the combined table is illustrative, not a rule guaranteeing exact convergence in every larger sample. Eye color involves several genes; this hypothetical cross illustrates probability under specified assumptions. A complete response also states the system boundary, units, matched conditions and limitations. Distinguish supplied illustrative outcomes from collected measurements, and explain why your revised mechanism fits the relevant evidence. Different observations should be interpreted rather than replaced to match the example.
Compare this model with the learner’s actual evidence. Different measurements can support a different conclusion; check the reasoning and limitations, not matching wording.