AP Biology Unit 5: Meiosis to Mendelian Genetics
Syllabus alignment: official course/syllabus source.
Learning targets
- Explain how meiosis transmits chromosomes and generates genetic variation.
- Predict genotype and phenotype probabilities from genetic crosses.
- Use data to justify inheritance claims in AP-style FRQ responses.
1 · Meiosis and variation
Homologous chromosomes pair in meiosis I. Crossing over can exchange DNA between nonsister chromatids, while independent assortment creates different maternal/paternal chromosome combinations. Meiosis II separates sister chromatids.
2 · Mouse genetics model
For a monohybrid cross Aa × Aa, genotype probabilities are 1/4 AA, 1/2 Aa, 1/4 aa. If A is completely dominant, phenotype probabilities are 3/4 dominant and 1/4 recessive.
Probability predicts expected proportions, not an exact outcome in a small litter.
Watch and focus
Pause after each major idea and write one sentence linking the visual evidence to the lesson objective.
Quick check
Exam-style practice
FRQ. A mouse breeder crosses two heterozygous mice. Of 80 offspring, 56 show the dominant phenotype and 24 show the recessive phenotype. State the expected recessive number and explain why observed data may differ from the expected value. [4]