Exam skills
What the paper asks you to do
- Construct genetic diagrams
- Use genotype and phenotype notation
- Interpret pedigrees and variation data
Continuity & environment
Inheritance
Move from chromosomes and genes to crosses, variation, selection and modern genetic interpretation.5090 syllabus routeConcept · skill · exam language
What to know
Build the topic around four anchors.
- 01DNA, genes and chromosomes
- 02Mitosis and meiosis
- 03Monohybrid inheritance
- 04Variation and selection
Common mistakes
Where marks disappear
- Writing allele symbols inconsistently
- Confusing gene with allele
- Giving ratios without showing a genetic cross
Structured practice
Answer these without looking back.
For each prompt, write the biological chain clearly enough that every mark-worthy link is visible.
- 01Complete a heterozygous monohybrid cross.
- 02Explain how meiosis produces variation.
- 03Interpret a simple pedigree.
Continue learning
Read the connected explanation.
Build genetic ratios from chromosome behaviour instead of memorising 3:1 and 9:3:3:1 as isolated formulas.
This independent teaching resource follows the Cambridge O Level Biology 5090 syllabus direction and is not endorsed by Cambridge International Education.