Allele pair grid
Build all four pairings in a declared one-gene model.
Adult planning suggestion: about 9–12 · Logic & rule checking
- Players
- 1–4 with adult support
- Time
- 15–25 minutes
- Materials
- A/a cards and 2×2 pairing table
Prepare
Use two fictional organisms, each modeled as Aa at one locus. Each contributes A or a with probability 1/2, independently. Assume A is completely dominant for a fictional trait. Do not use family information or claim this describes every real trait.
Play
Write one parent’s alternatives A,a above two columns and the other’s A,a beside two rows. Put one letter from each parent into each cell. Keep the parent origins visible even when writing Aa in conventional order.
Worked example
The four equally likely cells are AA,Aa,Aa,aa. Genotype proportions are 1/4,2/4,1/4; under the stated dominance assumption the dominant-appearance proportion is 3/4. The two Aa cells are distinct pairing outcomes.
Finish and check
Four offspring would not be guaranteed to match those four cells once each. A fresh independent pairing could repeat a cell. For a second paper cross Aa×aa, keep two a rows visibly separate: outcomes Aa,Aa,aa,aa give 1/2 each appearance.
Adaptation and limits
Finish after each cell can be traced to exactly one row and column label. Compare genotype with the modeled appearance, and state the independence and dominance assumptions. This is not a prediction about a student, family or health condition.
Purpose, observation and provenance
Within this activity: Build all four pairings in a declared one-gene model.
Trace every cell back to one parent row and column; keep the two heterozygote outcomes separate in counting.
Our rules, examples and printable diagrams are separately prepared. The earliest inventor of the broader mechanism is not established here.
OpenStax: Laws of Inheritance — Reference supports the stated concept; our fictional numbers, instructions and paper diagrams are independently prepared, not reproduced teaching pages.
Secondary practice: Cooperation and explaining a check.
For a class of 30, use ten groups of three. Prepare one player-material set per group and keep the host key with the adult. Rotate operator, recorder and checker after each worked example; a reader or scribe may help without choosing answers. Avoid public ranking or diagnostic labels.
Age bands are planning suggestions. Background references may address older learners and do not validate suitability for this age band. Goals describe observable actions, not measured long-term gains or institutional endorsement.
Free alternative: Copy the supplied grids, labels and cards onto reused paper. No specialist product is needed. Adults may prepare pieces or act as a scribe.
Printable materials
Preview at 100% scale, with browser headers and footers off. Cut with suitable help. Keep host keys separate. This is a manual tabletop kit, not an online opponent, automatic judge or solver.
Rules to keep beside the materials
- Use two fictional organisms, each modeled as Aa at one locus. Each contributes A or a with probability 1/2, independently. Assume A is completely dominant for a fictional trait. Do not use family information or claim this describes every real trait.
- Write one parent’s alternatives A,a above two columns and the other’s A,a beside two rows. Put one letter from each parent into each cell. Keep the parent origins visible even when writing Aa in conventional order.
- The four equally likely cells are AA,Aa,Aa,aa. Genotype proportions are 1/4,2/4,1/4; under the stated dominance assumption the dominant-appearance proportion is 3/4. The two Aa cells are distinct pairing outcomes.
- Four offspring would not be guaranteed to match those four cells once each. A fresh independent pairing could repeat a cell. For a second paper cross Aa×aa, keep two a rows visibly separate: outcomes Aa,Aa,aa,aa give 1/2 each appearance.
- Finish after each cell can be traced to exactly one row and column label. Compare genotype with the modeled appearance, and state the independence and dominance assumptions. This is not a prediction about a student, family or health condition.
Allele pair grid — player materials
| Aa × Aa | A | a |
|---|---|---|
| A | ||
| a |
| Aa × aa | A | a |
|---|---|---|
| a (1) | ||
| a (2) |
| Genotype | Outcomes /4 | Modeled appearance |
|---|---|---|
| ________ | ________ | ________ |
| ________ | ________ | ________ |
| ________ | ________ | ________ |
Host check — keep separate
Aa×Aa: AA,Aa,Aa,aa; Aa×aa: Aa,Aa,aa,aa.
Examples are stipulated model cases, not measured experimental or learning outcomes.