Inheritance

Worked examples (5)

• 1Sources of genetic variation in meiosis (5 marks)
• 2Monohybrid cross with Punnett square (4 marks)
• 3Dihybrid cross — F₂ 9:3:3:1 ratio (6 marks)
• 4Chi-squared test on dihybrid ratio (7 marks)
• 5Genotype vs phenotype (3 marks)

Model answers (5)

• ✓Model answer — 9700/42 May/Jun 2024 Q5 (adapted)
• ✓Model answer — 9700/42 Oct/Nov 2024 Q5(b) (adapted)
• ✓Model answer — Practice question — recurrent Paper 4 style
• ✓Model answer — 9700/42 May/Jun 2024 Q5(c) (adapted)
• ✓Model answer — 9700/42 Oct/Nov 2024 Q5(a) (adapted)

Worked examples (5)

• 1ABO blood groups — codominance + multiple alleles (5 marks)
• 2X-linked recessive (haemophilia) cross (6 marks)
• 3Recessive epistasis — Labrador coat colour (6 marks)
• 4X-linked: colour-blind father and unaffected mother (4 marks)
• 5Complete vs incomplete dominance vs codominance (3 marks)

Model answers (5)

• ✓Model answer — 9700/42 May/Jun 2024 Q6 (adapted)
• ✓Model answer — 9700/42 Oct/Nov 2024 Q6 (adapted)
• ✓Model answer — 9700/42 May/Jun 2024 Q6(c) (adapted)
• ✓Model answer — 9700/42 Oct/Nov 2024 Q6(b) (adapted)
• ✓Model answer — Practice question — recurrent Paper 4 style

Worked examples (5)

• 1The lac operon in absence and presence of lactose (8 marks)
• 2Why the lac operon is inducible (3 marks)
• 3Oestrogen as a transcription factor (5 marks)
• 4Homeobox (Hox) genes in development (5 marks)
• 5Comparing prokaryotic and eukaryotic gene control (5 marks)

Model answers (5)

• ✓Model answer — 9700/42 May/Jun 2024 Q7 (adapted)
• ✓Model answer — 9700/42 Oct/Nov 2024 Q7(a) (adapted)
• ✓Model answer — 9700/42 May/Jun 2024 Q7(b) (adapted)
• ✓Model answer — 9700/42 Oct/Nov 2024 Q7(b) (adapted)
• ✓Model answer — Practice question — recurrent Paper 4 style