Inheritance, Variation and Evolution: Exam Practice

This lesson brings together everything you have learned across the Inheritance, Variation and Evolution topic for AQA GCSE Biology. It provides exam technique guidance, common question types, and strategies for answering the most challenging questions. Use this lesson to consolidate your knowledge and prepare for the exam.

---

Key Topics to Revise

Before tackling exam questions, make sure you are confident with all the key areas:

Topic area	Key content
DNA and the genome	Structure of DNA, nucleotides, base pairing, chromosomes, genes, the Human Genome Project
Protein synthesis [H]	Transcription, translation, mRNA, tRNA, codons, amino acids, protein folding
Genetic inheritance	Dominant/recessive alleles, homozygous/heterozygous, Punnett squares, genotype, phenotype
Inherited disorders	Polydactyly (dominant), cystic fibrosis (recessive), genetic testing, ethics
Sex determination	Sex chromosomes (XX/XY), sex-linked inheritance [H]
Variation	Genetic variation, environmental variation, continuous vs discontinuous
Natural selection	Darwin's theory, evidence for evolution, antibiotic resistance, speciation
Selective breeding	Process, examples, advantages, disadvantages
Genetic engineering	Process, examples (insulin, Golden Rice), advantages, disadvantages, ethics
Classification	Linnaean system, binomial naming, three-domain system [H], extinction

Exam Tip: Create a checklist of all the topics above and tick them off as you revise each one. If you can explain each topic to someone else without looking at your notes, you truly understand it.

---

Common Question Types

Type 1: Definition Questions (1-2 marks)

These test whether you know precise definitions of key terms.

Example: Define the term "allele." (1 mark)

Model answer: An allele is a version/form of a gene.

Common terms tested:

Term	Definition
Gene	A section of DNA that codes for a specific protein
Allele	A version of a gene
Genotype	The combination of alleles an organism has
Phenotype	The observable characteristic
Homozygous	Having two identical alleles
Heterozygous	Having two different alleles
Dominant	An allele that is always expressed when present
Recessive	An allele only expressed when two copies are present
Mutation	A change in the base sequence of DNA
Genome	The entire set of genetic material in an organism
Evolution	A change in the inherited characteristics of a population over time
Species	A group of organisms that can interbreed to produce fertile offspring

Exam Tip: Definition questions are easy marks if you learn them precisely. Write concise, accurate definitions. Do not over-explain — a 1-mark question needs a 1-sentence answer.

---

Type 2: Punnett Square Questions (3-4 marks)

These ask you to predict offspring genotypes and phenotypes using a genetic diagram.

Approach:

1. Identify the alleles (e.g. B = dominant, b = recessive)
2. Write the parental genotypes
3. Identify the gametes each parent can produce
4. Draw and complete the Punnett square
5. State the genotype ratio
6. State the phenotype ratio and/or probability

Example: Two parents are both heterozygous for a gene controlling flower colour. Purple (P) is dominant to white (p). What proportion of offspring would you expect to have white flowers? (3 marks)

Model answer:

Parental genotypes: Pp x Pp

	P	p
P	PP	Pp
p	Pp	pp

Genotype ratio: 1 PP : 2 Pp : 1 pp Phenotype ratio: 3 purple : 1 white Proportion with white flowers: 1 in 4 (25%)

graph TD
    A[Parent 1: Pp] --> C[Gametes: P and p]
    B[Parent 2: Pp] --> D[Gametes: P and p]
    C --> E[Punnett square]
    D --> E
    E --> F[PP - Purple]
    E --> G[Pp - Purple]
    E --> H[Pp - Purple]
    E --> I[pp - White]

---

Type 3: Explain Natural Selection (4-6 marks)

These are extended response questions testing your understanding of how natural selection works.

Key steps to include:

1. There is variation in the population due to genetic differences
2. Some individuals have characteristics that give them a selective advantage in their environment
3. These individuals are more likely to survive (survival of the fittest)
4. They are more likely to reproduce and pass on their alleles to offspring
5. Over many generations, the frequency of the advantageous allele increases in the population
6. The population evolves

Common contexts:

• Peppered moths during the Industrial Revolution
• Antibiotic-resistant bacteria (MRSA)
• Darwin's finches on the Galapagos Islands
• Insecticide-resistant insects

Exam Tip: Never say organisms "choose" to evolve or "decide" to develop a trait. Natural selection acts on random variation that already exists. Saying organisms change "in order to survive" is also incorrect — the variation comes first, and those with the right variation survive.

---

Type 4: Evaluate Questions (6 marks)

These ask you to weigh up arguments for and against something, then reach a conclusion.

Common evaluate questions:

• Evaluate the use of embryo screening
• Evaluate the advantages and disadvantages of genetic engineering
• Evaluate selective breeding vs genetic engineering
• Evaluate the impact of antibiotic resistance on medicine

Structure for a 6-mark evaluate answer:

Paragraph	Content
1	Introduction — state what you are evaluating
2	Arguments FOR (with specific examples and explanations)
3	Arguments AGAINST (with specific examples and explanations)
4	Conclusion — weigh up the evidence and give a justified opinion

Example question: Evaluate the use of genetic engineering to produce crops with improved characteristics. (6 marks)

Model answer structure:

Arguments for:

• GM crops can be made pest-resistant (e.g. Bt crops), reducing pesticide use and environmental damage
• Golden Rice produces beta-carotene, helping to prevent vitamin A deficiency in developing countries
• GM crops can have higher yields, helping to feed a growing global population
• Crops can be made drought-resistant, valuable in areas affected by climate change

Arguments against:

• Long-term effects on human health are not fully understood
• GM genes could spread to wild plant populations through cross-pollination
• Large corporations patent GM seeds, making farmers dependent and unable to save seeds
• Ethical concerns — some people believe genetic modification is unnatural
• Could reduce biodiversity if GM monocultures replace diverse natural habitats

Conclusion: Genetic engineering offers significant benefits for food production and nutrition, but its risks need to be carefully managed through regulation, long-term testing, and transparent labelling.

---

Type 5: Analyse Data Questions (2-4 marks)

AQA frequently presents data in tables, graphs, or charts and asks you to interpret it.

Tips for data questions:

• Read the axes — make sure you know what is being measured
• Identify trends — is the data increasing, decreasing, or staying the same?
• Quote figures — always use specific numbers from the data to support your answer
• Explain the pattern — link the data to your scientific knowledge
• Consider anomalies — if one data point does not fit the trend, mention it

---

Common Mistakes to Avoid

Mistake	Correction
Confusing gene with allele	A gene is a section of DNA; an allele is a version of a gene
Saying organisms "choose" to evolve	Evolution is not a choice — it happens through random variation and natural selection
Writing Punnett squares incorrectly	Always separate alleles in gametes; each box should have one allele from each parent
Forgetting that ratios are probabilities	A 3:1 ratio does not mean exactly 3 out of 4 offspring will show the trait
Not showing working in calculations	Always show parental genotypes, gametes, and the Punnett square
Confusing transcription and translation	Transcription = DNA to mRNA (in nucleus); Translation = mRNA to protein (at ribosome)
Confusing dominant with "stronger" or "better"	Dominant simply means expressed when one copy is present; it does not mean the allele is superior
Writing alleles incorrectly for sex-linked traits	Always write the X and Y chromosomes (e.g. X^H Y, not just H)

Exam Tip: Before handing in your exam paper, quickly scan through your answers for these common mistakes. A two-minute check could save you several marks.

---

Six-Mark Question Framework

For extended response questions, use this framework: