Mastering Punnett Squares: Predicting Offspring

Mastering Punnett Squares: Predicting Offspring

Year 9 Science One Tree Hill College Understanding Genetics and Inheritance

WALT (We Are Learning To)

Understand key genetic terminology (genotype, phenotype, alleles) Distinguish between dominant and recessive alleles Construct and interpret Punnett squares Predict offspring ratios and probabilities Apply Māori perspectives on whakapapa (genealogy) and inheritance

Genetic Vocabulary - Te Reo Genetics

Phenotype = Physical appearance (atahua - what we can see) Genotype = Genetic makeup (taiao rauropi - genetic environment) Allele = Different versions of the same gene Dominant allele = Always expressed (represented by CAPITAL letter) Recessive allele = Only expressed when no dominant allele present (lowercase letter)

Homozygous vs Heterozygous

{"left":"Homozygous = Same alleles (AA or aa)\nExample: RR (red flowers)\nPurebred traits\nPredictable offspring","right":"Heterozygous = Different alleles (Aa)\nExample: Rr (red flowers, carries white)\nHybrid traits\nMore genetic variation"}

Setting Up a Punnett Square

Practice Time: Flower Color Cross

Parent Cross: Rr (red) × Rr (red) Set up your Punnett square Fill in all possible offspring combinations Calculate the ratios What percentage will be red? What percentage white?

Reading Punnett Square Results

Count each genotype: RR = 1, Rr = 2, rr = 1 Genotypic ratio = 1:2:1 Phenotypic ratio = 3:1 (3 red : 1 white) Probability calculations: 25% RR, 50% Rr, 25% rr Real-world application: Breeding programs and genetic counseling

Whakatōhea Wisdom

"He taonga tuku iho - Treasures handed down" Just as our ancestors passed down cultural treasures through whakapapa, genes are biological treasures passed from parents to offspring Understanding genetics helps us appreciate both our biological and cultural inheritance

Class Challenge: Eye Color Genetics

Brown eyes (B) are dominant to blue eyes (b) Cross: Bb × Bb Work in pairs to solve Present your results to the class Extension: What if one parent was BB?

Success Criteria & Next Steps

✓ Can define genotype and phenotype ✓ Can identify dominant and recessive alleles ✓ Can construct a basic Punnett square ✓ Can calculate genetic ratios and percentages Next lesson: Multiple trait inheritance (dihybrid crosses) Extension: Research genetic disorders and inheritance patterns