Biology, genetics and evolution (inheritance, chromosomes, DNA and…

Genes and Traits: Heredity and Punnett Squares Grades 7–8 · partly supports this outcome

Why you look like your family but not exactly, how two purple-flowered pea plants can have a white-flowered one, what Gregor Mendel really counted, and what happens when a gene changes. Four no-materials lessons with printed allele cards, Punnett squares, Mendel's own data and a real gene to decode.

• Why do you look like your family, but not exactly? 45–60 min

  Teams build baby dragons by flipping printed allele coin cards from two parents, then bud copies of one parent and compare the two litters. They explain genes, alleles and chromosomes, and why sexual reproduction makes variety while asexual reproduction makes copies.

• How can two purple-flowered pea plants have a white-flowered one? 45–60 min

  Students play pea plants, passing allele slips from behind their backs to make offspring, then draw Punnett squares for three crosses and solve four case files. They explain dominant and recessive alleles, genotype and phenotype, and why most human traits do not follow these simple rules.

• What did Mendel count? 45–60 min

  Teams rotate around seven data stations with Gregor Mendel's real pea counts from 1866, work out each ratio, and compare it with the 3 to 1 a Punnett square predicts. A card of ten single plants shows how much small samples wobble, so students explain heredity as probability, not certainty.

• What happens when a gene changes? 45–60 min

  Students decode the first words of the real human haemoglobin gene, apply five mutation cards and see which changes alter the protein. Then they stand in the corner of the room that matches each real case: harmful, neutral, helpful or it depends. They explain how a change in a gene can change a protein and a trait.