OCR A 6.1.3 · 20 written questions · 44 marks · about 55 minutes · marked as you go
This free quiz has 20 written exam questions on manipulating genomes, all taken from OCR A Level Biology A papers (A level, 2018 to 2025). Short answers mark themselves. For longer answers you write your answer, then tick off the OCR mark-scheme points you made, so you see exactly where the marks are. Twenty real OCR A Level exam questions across the whole of 6.1.3, from DNA sequencing and bioinformatics through DNA profiling, PCR and electrophoresis to genetic engineering, ethics and gene therapy.
What the quiz covers (OCR A spec 6.1.3)
DNA sequencing and bioinformatics (6.1.3(a)(b)): defining DNA sequencing, newer high-speed sequencing methods, predicting amino acid sequences from DNA, comparing genomes with bioinformatics and how synthetic biology can provide new medicines.
DNA profiling (6.1.3(c)): other uses of DNA profiling, interpreting peaks at different loci, judging how strongly a profile match supports a claim, and a paternity case.
PCR (6.1.3(d)): the three temperature steps of a PCR cycle, why the extension temperature suits Taq polymerase, and a log calculation of how many fragments PCR produces.
Electrophoresis (6.1.3(e)): the solutions needed in an electrophoresis tank and improving a student's flawed electrophoresis procedure.
Genetic engineering (6.1.3(f)): the enzymes and methods used to make recombinant plasmids and get them into bacteria, screening for transformed bacteria, and comparing CRISPR gene editing with traditional genetic engineering.
Ethics and gene therapy (6.1.3(g)(h)): patents on GM crops, differences between somatic and germ-line gene therapy, and why gene therapy is unlikely to work for a disease caused by a dominant allele.
How to use it
Write every answer in full, as you would in the exam: the mark for each question is shown, so you know how much to write. When you self-mark, only tick a point if your answer clearly makes it, then read the examiner's tip under each question. Your progress is saved on your device, so you can do it in two sittings, and at the end you can retry just the questions where you dropped marks.
Prefer multiple choice? Try the 20-question Cellular Control and Manipulating Genomes multiple choice quiz first.
Open the Manipulating Genomes quiz in a new tab (easier on a phone)
Where students lose marks (from OCR examiners' reports and mark schemes)
Each point below is followed by wording that gained marks.
Nucleotides, not base pairs: Defining DNA sequencing as finding the order of 'base pairs', or of amino acids. OCR ignores 'base pairs', and DNA isn't made of amino acids.
✔ Gains credit: Working out the sequence (order) of nucleotides (bases) in DNA.
Three bases, one amino acid: Describing how sequencing is done when asked how it lets you predict a polypeptide, or mixing up bases with amino acids.
✔ Gains credit: The sequence of bases codes for the sequence of amino acids; each triplet (codon) codes for one amino acid.
Synthetic biology means redesigning organisms: Describing personalised medicine or computer modelling of drugs when asked about synthetic biology.
✔ Gains credit: Genetically modifying a named organism so it produces a named drug, therapeutic protein or vaccine, e.g. insulin or artemisinin.
Homozygous, not homologous: Explaining one or two peaks on a DNA profile with muddled terms: gene for allele, homologous for homozygous, polygenic for polymorphic.
✔ Gains credit: Two peaks: heterozygous at that locus (two different alleles). One peak: homozygous (the same allele twice).
Say identical twins: Suggesting a matching DNA profile could belong to the suspect's twin without saying what kind of twin, or only listing reasons the match is convincing.
✔ Gains credit: Only six loci were compared, so a close relative could match; an identical (monozygotic) twin would have the same profile.
Remember the DNA ladder: Naming only a buffer and a dye as the extra solutions for electrophoresis, or giving a solution without its purpose.
✔ Gains credit: Reference (marker) DNA of known fragment lengths, to compare with and identify the size of the sample fragments.
Taq polymerase is thermostable: Writing generally about enzymes and optimum temperatures without naming the enzyme or saying why it suits PCR.
✔ Gains credit: Taq polymerase comes from thermophilic bacteria (hot springs), so it doesn't denature at the high temperatures of PCR.
Small sample, so amplify: Saying PCR is needed 'to amplify the sample' or 'to get a big enough sample', which just restates what PCR does.
✔ Gains credit: The initial crime scene sample is small: there is not much DNA to begin with.
Keep practising
Try the Cellular Control and Manipulating Genomes multiple choice quiz, the Genetics and Evolution multiple choice quiz, the Patterns of Inheritance written quiz or the Cloning and Biotechnology written quiz, or browse all our OCR A Level Biology quizzes. Our OCR A masterclasses (Year 12 on Wednesdays at 5.15pm, Year 13 on Tuesdays at 6.30pm) work through real exam questions on one topic each week.
Questions, mark schemes and examiners' report extracts © OCR.