Practise 42 exam-style questions on The understanding of genetics (biology only) for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
42 questions
4–5 marks each
Instant marking
No sign-up needed
20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
4 marks
Give two examples of evidence (other than DNA) that supports the theory of evolution.
Model answer
Fossil record showing transitional forms; comparative anatomy (homologous structures); biogeography (distribution of species); comparative embryology.
Explanation
Multiple lines of non-molecular evidence support evolution: fossils document change over time and transitional forms, homologous structures indicate common ancestry, geographical distributions match evolutionary history, and embryos of related species show conserved patterns.
Mark scheme
1 mark
fossil record / transitional fossils
1 mark
homologous structures / comparative anatomy
1 mark
biogeography / distribution of species
1 mark
comparative embryology / early development similarities
Question 2
4 marks
Mendel used pea plants with clear contrasting characters. Explain why choosing clear, discrete traits made his experimental results easier to interpret.
Model answer
Discrete traits (e.g., round vs wrinkled seeds) show distinct phenotypic categories, producing clear ratios in crosses that reveal patterns of inheritance. Continuous traits would produce overlapping phenotypes making ratios and inheritance patterns harder to detect.
Explanation
Mendel’s careful choice of discontinuous, easily scored traits produced unambiguous data and simple ratios that exposed underlying genetic laws; variable quantitative traits would have obscured such patterns.
Mark scheme
1 mark
discrete traits produce distinct categories
1 mark
results gave clear ratios that revealed inheritance patterns
1 mark
continuous traits would overlap and be harder to analyse
1 mark
reduced environmental influence on trait expression
Accept as reason if stated.
Question 3
5 marks
A population of insects is exposed to a new pesticide. Describe how antibiotic/pesticide resistance can develop in a population and spread.
Model answer
Random mutations produce some resistant individuals. Pesticide kills susceptible ones while resistant survive and reproduce. The resistance allele increases in frequency by natural selection. Gene flow or reproduction spreads the resistance through the population; if resistance has a genetic basis it becomes common.
Explanation
Resistance typically starts from rare genetic mutations; pesticide pressure preferentially removes susceptible individuals so resistant ones survive and breed, increasing the frequency of resistance genes and allowing resistance to spread through the population.
Mark scheme
1 mark
random mutation produces resistant individuals
1 mark
pesticide kills susceptible individuals so resistant survive (selection)
1 mark
survivors reproduce and pass resistance allele to offspring
1 mark
resistance allele increases in frequency over generations
1 mark
spread via reproduction / migration / gene flow
Question 4
5 marks
Explain how horizontal gene transfer (HGT) complicates reconstruction of evolutionary histories, especially in microbes.
Model answer
HGT moves genes between unrelated organisms, so different genes in the same organism may have different histories. This obscures tree-like relationships and makes genome trees discordant; HGT is common in microbes (plasmids, transduction) so phylogenies based on a single gene may be misleading.
Explanation
Because microbes frequently exchange genes across lineages, phylogenies based on genome sequences can show conflicting signals; HGT therefore makes reconstructing clear ancestry more complex and requires methods that account for gene transfer.
Mark scheme
1 mark
HGT transfers genes between unrelated organisms
1 mark
organism’s genes can have different evolutionary origins
1 mark
tree-like phylogeny is blurred; different genes give different trees
1 mark
common in microbes via plasmids, viruses (transduction), transformation
1 mark
so using single-gene phylogenies can be misleading for microbes
Ready to try the rest? Every answer you write is marked against the mark scheme, so you can see exactly where the marks are.
Ctrl + Enter to check
AI TutorHints first, answers after you try
Hi! Stuck? Ask me for a hint and I’ll help you work it out. Once you’ve checked your answer I can explain exactly where the marks are.
