OCR Gateway GCSE Biology A: Genes, inheritance and selection (B5) overview
An overview of the genes, inheritance and selection content (topic B5) in OCR Gateway GCSE Biology A (J247), mapping reproduction and meiosis, DNA the genome and variation, protein synthesis, genetic inheritance and Punnett squares, natural selection and evolution, and selective breeding and genetic engineering, and how they are examined on the second biology paper.
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The fifth biology topic of OCR Gateway GCSE Biology A (specification J247) is about genetics: how characteristics are inherited, how organisms vary, and how populations change over time. B5 Genes, inheritance and selection is examined on the second biology paper (J247/02 at Foundation, J247/04 at Higher). This page maps the topic and links to a focused answer page for each part.
The genes, inheritance and selection content
- Reproduction and meiosis
- Sexual and asexual reproduction, the formation of gametes by meiosis, how meiosis halves the chromosome number and gives variation, and the advantages of each type. See Reproduction and meiosis.
- DNA, the genome and variation
- The double helix and complementary base pairing, the genome and the value of sequencing it, and the genetic and environmental causes of variation including mutation. See DNA, the genome and variation.
- Protein synthesis
- Transcription of a gene into mRNA, translation at the ribosome, the triplet code, and how mutations change a protein (mainly Higher tier). See Protein synthesis.
- Genetic inheritance
- Alleles, genotype and phenotype, homozygous and heterozygous, Punnett squares and ratios, the inheritance of sex, and single-gene disorders. See Genetic inheritance.
- Natural selection and evolution
- Darwin's theory, antibiotic-resistant bacteria, the evidence from fossils, extinction, and the formation of new species. See Natural selection and evolution.
- Selective breeding and genetic engineering
- Artificial selection and its risks, the process and uses of genetic engineering, GM crops and bacteria making insulin, and cloning. See Selective breeding and genetic engineering.
How this topic is examined
Topics B4 to B6 are assessed on the second biology paper, which is 1 hour 45 minutes, worth 90 marks and 50% of the GCSE. Questions include multiple choice, short structured answers, genetic-cross calculations (Punnett squares, ratios and probabilities), data and evidence questions, and six-mark extended responses such as explaining natural selection or evaluating genetic engineering. The paper assumes the B1 to B3 content and includes synoptic questions, and every paper also tests the B7 practical skills.
How to study the genes, inheritance and selection topic
- Work from the specification statements. Each point is a checklist; questions are written from them.
- Separate meiosis and mitosis. Know what each does and where, and why meiosis gives variation.
- Drill Punnett squares. Practise giving both the phenotype and genotype ratios and probabilities until they are automatic.
- Learn the sequences. The steps of natural selection and of genetic engineering are marked on a logical order.
- Rehearse evaluate questions. Genetic modification and selective breeding need balanced answers covering benefits and risks.
For the official specification
OCR publishes the full specification, past papers and mark schemes at ocr.org.uk. Always revise from the current specification and OCR's own past papers, because question style is board-specific.