IGCSE Biology: Inheritance – Exam Tips & Revision Guide
This guide covers IGCSE Biology topic 17: inheritance. You will revise chromosomes, genes, DNA (structure and role), genetic diagrams (monohybrid cross), dominant and recessive alleles, and phenotype vs genotype.
Key concepts to revise
- Chromosomes – In nucleus; carry genes; come in pairs (diploid); one from each parent.
- Gene – Section of DNA; codes for a characteristic; different forms = alleles (e.g. T and t).
- Dominant / Recessive – Dominant allele expressed if present (T); recessive only if two copies (tt).
- Genetic diagram – Punnett square; parental genotypes (e.g. Tt × Tt); offspring genotypes and phenotypes; ratio (e.g. 3 : 1).
Exam tips and command words
- State – Where genes are found (on chromosomes); what a gene codes for (a characteristic/protein).
- Draw a genetic diagram – Show parental genotypes, gametes, offspring genotypes and phenotypes; give ratio.
- Calculate – Probability of offspring having a genotype or phenotype (e.g. 1/4, 3/4).
- Define – Genotype (alleles present); phenotype (visible characteristic); dominant; recessive.
Common mistakes
- Confusing genotype (e.g. Tt) with phenotype (e.g. tall).
- Not showing gametes in the diagram (e.g. T and t from Tt parent).
- Writing ratio as “3 tall : 1 short” without stating it is phenotype ratio.
Revision checklist
- Define chromosome, gene, allele, genotype, phenotype, dominant, recessive.
- Draw a monohybrid cross (e.g. Tt × Tt) and state offspring genotype and phenotype ratios.
- State where genes and DNA are found and the role of DNA (codes for proteins).
- Calculate probability of offspring having a given characteristic from a genetic cross.
Next steps
Book a free trial with an IGCSE Biology tutor to practise genetic diagrams and inheritance questions, or explore Tutopiya’s learning portal for more revision resources.
Ready to Excel in Your Studies?
Get personalised help from Tutopiya's expert tutors. Whether it's IGCSE, IB, A-Levels, or any other curriculum — we match you with the perfect tutor and your first session is free.
Book Your Free TrialWritten by
Tutopiya Team
Educational Expert
Related Articles
Cambridge IGCSE Biology (0610): Topics, Past Paper Practice and Common Mistakes
Cambridge IGCSE Biology 0610: the 21 topics, how Papers 1 to 6 work, how to practise past papers properly and the mistakes examiners report most often.
Cambridge IGCSE Biology: A Revision Plan for Nigerian Students
A week-by-week Cambridge IGCSE Biology revision plan for Nigerian students sitting 0610 in May/June 2027, built on the final timetable and 2026–2028 syllabus.
Cambridge IGCSE Fees in Nigeria for 2027: What One Subject Costs and How to Avoid Late Fees
Cambridge IGCSE fees in Nigeria for 2027 planning: latest British Council fees per subject, how late-fee stages work, extra costs and a checklist to avoid them.