plumiPatterns of inheritance: OCR A‑Level Biology B questions
Every OCR A-Level Biology B exam question on 5.1.1 Patterns of inheritance, 2016–2025, with its mark scheme and examiner’s report.
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Q5(c)(i)
The whole paper ↗![June 2025 Paper 2, question 5(c)(i): Describe how trisomy 21 occurs. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42202-jun25-05-ci-qp.webp?v=3)
Q5(c)(ii)
The whole paper ↗![June 2025 Paper 2, question 5(c)(ii): Describe one other way in which Down’s syndrome can be caused. [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42202-jun25-05-cii-qp.webp?v=3)
Q5(d)(i)
The whole paper ↗![June 2025 Paper 2, question 5(d)(i): Suggest and explain a reason for this. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42202-jun25-05-di-qp.webp?v=3)
Q5(d)(ii)
The whole paper ↗![June 2025 Paper 2, question 5(d)(ii): Describe two ways in which an older couple can reduce the risk of having a child with Down’s syndrome. 1 2 [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42202-jun25-05-dii-qp.webp?v=3)
Q5(d)(iii)
The whole paper ↗![June 2025 Paper 2, question 5(d)(iii): Identify one ethical issue associated with either of your answers to part (ii). [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42202-jun25-05-diii-qp.webp?v=3)
Q1(a)(i)
The whole paper ↗![June 2024 Paper 2, question 1(a)(i): Define the term genotype. [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42202-jun24-01-ai-qp.webp?v=3)
Q1(a)(ii)
The whole paper ↗![June 2024 Paper 2, question 1(a)(ii): Define the term phenotype. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42202-jun24-01-aii-qp.webp?v=3)
Q1(b)(i)
The whole paper ↗![June 2024 Paper 2, question 1(b)(i): Explain one piece of evidence from Fig. 1.1 that indicates the allele for blue eyes is recessive. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42202-jun24-01-bi-qp.webp?v=3)
Q1(b)(ii)
The whole paper ↗![June 2024 Paper 2, question 1(b)(ii): Explain one piece of evidence from Fig. 1.1 that indicates the allele for blue eyes is located on an autosome and not the X chromosome. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42202-jun24-01-bii-qp.webp?v=3)
Q1(b)(iii)
The whole paper ↗
Q1(b)(iv)
The whole paper ↗![June 2024 Paper 2, question 1(b)(iv): Suggest why the χ2 test would not be appropriate for analysing the data in Fig. 1.1. [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42202-jun24-01-biv-qp.webp?v=3)
Q1(c)(i)
The whole paper ↗![June 2024 Paper 2, question 1(c)(i): Use the information in the Advance Notice Article to explain why this conclusion is not supported. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42202-jun24-01-ci-qp.webp?v=3)
Q1(c)(ii)
The whole paper ↗![June 2024 Paper 2, question 1(c)(ii): Suggest an explanation for the child’s brown eyes that is supported by the information in the Advance Notice Article. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42202-jun24-01-cii-qp.webp?v=3)
Q2(a)
The whole paper ↗
Q4(b)(i)
The whole paper ↗![June 2023 Paper 3, question 4(b)(i): Calculate χ2 for the results shown in Table 4.1. Use the formula: 2 ( ) f f - / χ2 = o e f e Give your answer to 3 significant figures. χ2 = [3]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h42203-jun23-04-bi-qp.webp?v=3)
All 53 questions on Patterns of inheritance, as a list
- June 2025, Paper 1, Q24 (1 mark): A sequence of nucleotide bases in a DNA coding strand is shown below. TCA-TGG-CTG-GGC-CTC-GCC-TCC Which of the following statements is/are correct? 1 A substitu
- June 2025, Paper 1, Q25 (1 mark): The diagrams of chromosomes show the positions of genes S and T. Gene S Gene S Gene T Gene T Gene S Gene T Gene T Gene S A B C D Which of the diagrams shows aut
- June 2025, Paper 2, Q5(c)(i) (2 marks): Describe how trisomy 21 occurs. [2]
- June 2025, Paper 2, Q5(c)(ii) (1 mark): Describe one other way in which Down’s syndrome can be caused. [1]
- June 2025, Paper 2, Q5(d)(i) (2 marks): Suggest and explain a reason for this. [2]
- June 2025, Paper 2, Q5(d)(ii) (2 marks): Describe two ways in which an older couple can reduce the risk of having a child with Down’s syndrome. 1 2 [2]
- June 2025, Paper 2, Q5(d)(iii) (1 mark): Identify one ethical issue associated with either of your answers to part (ii). [1]
- June 2024, Paper 1, Q13 (1 mark): The diagram shows how a chromosome mutation results in a child having a syndrome. Father Mother Fertilisation Which of the statements about the diagram is corre
- June 2024, Paper 2, Q1(a)(i) (1 mark): Define the term genotype. [1]
- June 2024, Paper 2, Q1(a)(ii) (2 marks): Define the term phenotype. [2]
- June 2024, Paper 2, Q1(b)(i) (2 marks): Explain one piece of evidence from Fig. 1.1 that indicates the allele for blue eyes is recessive. [2]
- June 2024, Paper 2, Q1(b)(ii) (2 marks): Explain one piece of evidence from Fig. 1.1 that indicates the allele for blue eyes is located on an autosome and not the X chromosome. [2]
- June 2024, Paper 2, Q1(b)(iii) (2 marks): The chi squared (χ2) test is used to determine whether the results of genetic crosses are statistically significant. Explain why the χ2 test is appropriate for
- June 2024, Paper 2, Q1(b)(iv) (1 mark): Suggest why the χ2 test would not be appropriate for analysing the data in Fig. 1.1. [1]
- June 2024, Paper 2, Q1(c)(i) (2 marks): Use the information in the Advance Notice Article to explain why this conclusion is not supported. [2]
- June 2024, Paper 2, Q1(c)(ii) (2 marks): Suggest an explanation for the child’s brown eyes that is supported by the information in the Advance Notice Article. [2]
- June 2024, Paper 3, Q2(a) (2 marks): NGLY1 deficiency is a rare disease caused by mutation in the NGLY1 gene. People with NGLY1 deficiency produce faulty N-glycanase 1, which is an enzyme that remo
- June 2023, Paper 1, Q16 (1 mark): Parents with a genetic disorder in either family are advised to undergo a pre-conceptual analysis so that genetic counsellors can assess the probability of thei
- June 2023, Paper 1, Q21 (1 mark): Which of the statements about allele mutations is / are correct? 1 They always cause a change in the DNA sequence. 2 They always cause a change to the sequence
- June 2023, Paper 3, Q4(b)(i) (3 marks): Calculate χ2 for the results shown in Table 4.1. Use the formula: 2 ( ) f f - / χ2 = o e f e Give your answer to 3 significant figures. χ2 = [3]
- June 2023, Paper 3, Q4(b)(ii) (3 marks): A χ2 probability table is shown in Table 4.2. Table 4.2 Degrees Probability (p) of freedom 0.10 0.05 0.01 1 2.71 3.84 6.64 2 4.60 5.99 9.21 3 6.25 7.82 11.34 4
- June 2023, Paper 3, Q4(c) (2 marks): Another aspect of rabbit fur colour is colour density. One gene controls colour density. This gene has several alleles, including: CF, which results in full col
- June 2023, Paper 3, Q4(d)(i) (1 mark): Rabbits can inherit genetic diseases. The probability of a rabbit inheriting a genetic disease can be assessed. Name the method used for assessing the risk of a
- June 2022, Paper 1, Q15 (1 mark): Which of the options is a correct definition of the genetic term it describes? A Genotype is the genetic composition of an organism. B Heterozygous is having tw
- June 2022, Paper 1, Q16 (1 mark): A group of students were investigating the inheritance of eye colour in Drosophila melanogaster, fruit flies. • The gene for eye colour is sex-linked. • The all
- November 2021, Paper 1, Q19 (1 mark): Two heterozygous individuals with the genotype, HhRr, were crossed during an investigation of dihybrid inheritance. Which of the options, A to D, shows the prob
- November 2021, Paper 1, Q32(d)(iii) (1 mark): Obesity, syndactyly, diabetes and kidney failure are other symptoms associated with BBS. Suggest why BBS is described as a syndrome. [1]
- November 2020, Paper 1, Q32(a) (2 marks): Suggest one advantage and one disadvantage of using D. melanogaster over P. sativum as a model organism. advantage disadvantage [2]
- November 2020, Paper 1, Q32(b)(i) (1 mark): Two plants, both heterozygous for each trait, were crossed. State the genotype of the parental plants using the letters R for plant height and Y for flower colo
- November 2020, Paper 1, Q32(b)(ii) (4 marks): Crossing of the parental plants produced 320 offspring. The numbers of offspring with each phenotype are shown in the table below. (O – E)2 Observed Expected (O
- November 2020, Paper 1, Q32(b)(iii) (2 marks): The table below is a χ 2 significance table. p% 99 97.5 95 90 10 5.0 2.5 1.0 0.5 v = 1 0.0001 0.0010 0.0039 0.0158 2.706 3.841 5.024 6.635 7.879 2 0.0201 0.0506
- November 2020, Paper 1, Q32(c) (2 marks): Scientists often model human genetic diseases, such as Huntington’s disease, in D. melanogaster. Describe the genetic basis of Huntington’s disease. [2]
- June 2019, Paper 1, Q18 (1 mark): A couple have a child. Both parents are heterozygous for the cystic fibrosis allele. Which of the options, A to D, is the probability that the child will have c
- June 2019, Paper 2, Q1(a)(i) (2 marks): State what is meant by the following genetic terms. 1. Gene 2. Allele [2]
- June 2019, Paper 2, Q1(c) (3 marks): Some genetic diseases, such as sickle cell anaemia, are caused by single mutations. Explain how a single gene mutation causes sickle cell anaemia. [3]
- June 2019, Paper 2, Q1(d) (4 marks): The goal of the researchers at the International Myeloma Foundation is to identify people who develop multiple myeloma after having monoclonal gammopathy of und
- June 2019, Paper 2, Q5(c) (2 marks): Red-green colour blindness is a sex-linked inherited disorder that affects mostly males. Suggest why red-green colour blindness affects mostly males. [2]
- June 2019, Paper 2, Q6(a)(ii) (1 mark): Errors in meiosis can lead to chromosome mutations. State the name of an event in meiosis that leads to chromosome mutations. [1]
- June 2019, Paper 2, Q6(a)(iii) (1 mark): State the name of one syndrome caused by a chromosome mutation. [1]
- June 2019, Paper 2, Q7(c)(i) (2 marks): Two pure breeding strains of maize were crossed. One strain had smooth yellow kernels. The other strain had wrinkled colourless kernels. All the kernels of the
- June 2019, Paper 2, Q7(c)(ii) (2 marks): Using a genetic diagram and your answer to (c)(i), predict the phenotypic ratio that you would expect from the second cross. phenotypic ratio: [2]
- June 2019, Paper 2, Q7(c)(iii) (3 marks): The actual results of the second cross are shown in Table 7.1. Number of Phenotype kernels Smooth yellow 275 Wrinkled yellow 277 Smooth colourless 235 Wrinkled
- June 2019, Paper 2, Q7(c)(iv) (1 mark): Table 7.2 shows a |2 probability table. Probability (p) Degrees of freedom 0.50 0.10 0.05 0.01 0.001 1 0.46 2.71 3.84 6.64 10.83 2 1.39 4.61 5.99 9.21 13.82 3 2
- June 2019, Paper 2, Q7(c)(v) (2 marks): Suggest an explanation for your conclusion in part (iv). [2]
- June 2018, Paper 1, Q19 (1 mark): Which of the options, A to D, describes the type of gene mutation that causes Huntington’s disease? A change of nucleotide that affects the protein B change of
- June 2018, Paper 1, Q31(a)(i) (1 mark): With reference to Fig. 31.2, suggest why the mother does not have Down’s syndrome. [1]
- June 2018, Paper 1, Q31(a)(ii) (4 marks): The child is born with Down’s syndrome. Complete the diagram in Fig. 31.2 to show the genetic material with respect to chromosomes 14 and 21 in: • the somatic c
- June 2018, Paper 1, Q31(b) (3 marks): Down’s syndrome is more commonly caused by a genetic event that is distinct from that shown in Fig. 31.1. State the name of this event and outline how it arises
- June 2018, Paper 2, Q2(d)(i) (2 marks): Use your knowledge of inheritance to suggest why it is difficult to study the genetic basis of drought resistance. [2]
- June 2017, Paper 1, Q15 (1 mark): The chi-squared (χ2) test was used to determine whether the inheritance pattern of a dihybrid cross was statistically significant. Four phenotypes were produced
- June 2017, Paper 1, Q31(a) (1 mark): Describe the type of DNA mutation that causes the amino acid change in the beta polypeptide. [1]
- June 2017, Paper 1, Q31(b)(i) (2 marks): Explain how a genetic counsellor can use knowledge of family history to provide genetic advice to the couple. [2]
- June 2017, Paper 1, Q31(b)(ii) (2 marks): Suggest two ethical concerns that may be associated with the genetic testing of embryos for sickle cell anaemia. 1 2 [2]
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