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Science · Grade 9

Heredity and Genetic Models

Learners explain how meiosis makes haploid gametes and shuffles alleles, then use Mendel's model, Punnett squares and the rules of probability to predict monohybrid and dihybrid crosses as fractions and expected counts. They extend the model to incomplete dominance, codominance, multiple alleles and sex-linked traits, and finish by reading pedigrees to infer how a trait is inherited and to calculate family probabilities.

  • 5 lessons
  • About 125 minutes
  • Heredity and genetic models check: 12 questions
  • Ways to answer: choose an answer, type a fraction, highlight a text, match pairs, type a number and place on a number line
See plans Included with Family, Teacher and School plans. Open in PlayOwl

What learners will discover

  • Explain how meiosis produces haploid gametes and genetic variation (crossing over, independent assortment, random fertilisation), contrast it with mitosis, and calculate chromosome numbers and combinations.
  • Use Mendel's model (alleles, dominance, genotype, phenotype) and Punnett squares to predict monohybrid crosses and test crosses as probabilities and expected numbers.
  • Predict dihybrid outcomes with Punnett squares and the product rule, for genes that assort independently.
  • Predict outcomes for incomplete dominance, codominance, multiple alleles (ABO blood groups) and X-linked traits.
  • Interpret pedigrees to infer the mode of inheritance and genotypes, and calculate probabilities for family members.

Lessons

  1. Meiosis and gametes 9 steps5 practiceabout 24 min
  2. Mendel's model and monohybrid crosses 9 steps6 practiceabout 26 min
  3. Two genes at once: dihybrid crosses and probability 9 steps6 practiceabout 24 min
  4. Beyond simple dominance 9 steps6 practiceabout 27 min
  5. Reading pedigrees 8 steps5 practiceabout 24 min
  6. Heredity and genetic models check 12 questions at the end

Keep exploring

More 9th grade science

Guide for grown-ups