Source: https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-4-multiple-alleles-and-epistasis [Revision notes](https://senecalearning.com/en-gb/revision-notes.md) › [A Level](https://senecalearning.com/en-gb/revision-notes/a-level.md) › [Biology](https://senecalearning.com/en-gb/revision-notes/a-level/biology.md) › [AQA](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa.md) › Multiple Alleles & Epistasis # Multiple Alleles & Epistasis Biology: AQA A Level, topic 7.1.4 ## Multiple Alleles Although only two alleles per gene are found in an individual diploid organism, there may be multiple alleles at the population level. This means many possible combinations of alleles can exist. ### Homologous chromosomes ![Homologous chromosomes](https://image-v2.cdn.app.senecalearning.com/2018-09/5270b392-8c2f-4ff1-9609-91b505c63d93/chromosomes-2817314_1280.png) - Chromosomes in diploid organisms exist in homologous pairs. - Homologous chromosomes consist of the same genes in the same order. - The only variation between homologous chromosomes is in the alleles. - Two alleles can be present for one gene. ### Multiple alleles ![Multiple alleles](https://image-v2.cdn.app.senecalearning.com/2018-08/e0907467-7279-4478-aea3-14752d4e00b4/eye-1173863_1920.jpg) - Although only two alleles can be present in an organism, there could be multiple different alleles for a single gene. - Multiple alleles provide many different genotype combinations. - This creates large variation at the population level. ### Rabbit coat colour ![Rabbit coat colour](https://image-v2.cdn.app.senecalearning.com/2018-03/4d71bdaa-7191-455b-9bde-9f2f13e8bc71/shutterstock_1024736800.jpg) - Four phenotypes exist for the c gene (coat colour): - CC - brown fur. - cchcch - blacktipped white fur. - chch - black fur on the extremities and white fur elsewhere. - cc - white fur. ### Dominance hierarchy ![Dominance hierarchy](https://image-v2.cdn.app.senecalearning.com/2018-08/1618f2af-fb32-440c-a953-c41eaaffe866/rabbits-field.jpg) - Multiple alleles have a dominance hierarchy. - E.g. rabbit coat colour. - CC is dominant over all other allele combinations. - cchcch is incompletely dominant over chch and cc. - chch is dominant over cc. ## Epistasis Multiple genes act in unison to produce the phenotype of an organism. Epistasis is when a gene at one locus inhibits the expression of a gene at another locus. Epistasis can be dominant or recessive. ### Function of epistasis ![Function of epistasis](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/6.1.2%20-%20DNA/dna-163466_640-min.jpg) - A gene at one location can mask the expression of another gene. This is called epistasis. - The alleles that are being masked are hypostatic to the epistatic alleles. - Epistasis often involves a pathway where expression of one gene is dependent on the function of another gene. ### Recessive epistasis ![Recessive epistasis](https://image-v2.cdn.app.senecalearning.com/2018-09/4b186ca4-f726-4543-bcc0-07454ac2bfb6/two-cameras-copies.jpg) - Recessive epistasis is where the epistatic allele (the allele that masks another gene) is recessive. - This means two copies of the epistatic allele must be present for expression of the hypostatic allele to be affected. ### Mouse coat colour ![Mouse coat colour](https://image-v2.cdn.app.senecalearning.com/2018-09/2468c2f0-e096-432e-99f1-ba078a6717ac/mouse-brown-coat.jpg) - Agouti (AA, Aa) coat colour is dominant to solid-coloured fur (aa) in mice. - The epistatic gene (C) is necessary for pigment production. - If a mouse is homozygous recessive (cc), no pigment is produced and the mouse coat colour is albino regardless of the A alleles. - If two heterozygotes (AaCc) are crossed, the offspring phenotypic ratio will be: - 9 agouti; 3 solid-coloured; 4 albino. ### Dominant epistasis ![Dominant epistasis](https://image-v2.cdn.app.senecalearning.com/2018-09/3c62e407-0ec8-49c7-878f-7cc209a23337/one-camera.jpg) - Dominant epistasis is where the epistatic allele is dominant. - This means only one copy of the epistatic allele must be present for expression of the hypostatic allele to be affected. ### Squash fruit colour ![Squash fruit colour](https://image-v2.cdn.app.senecalearning.com/2018-09/b1914d35-1d54-4f29-9f0d-bb36a5d7bf10/squash.jpg) - Yellow fruit (YY, Yy) is dominant to green fruit (yy). - The epistatic gene (W) is necessary for pigment production in the fruit. - If a squash has one copy of the dominant W allele (WW or Ww), the fruit is white regardless of the Y alleles. - If two heterozygotes are crossed (WwYy), the offspring phenotypic ratio will be: - 12 white; 3 yellow; 1 green. ## Test yourself on Multiple Alleles & Epistasis - Which of the following statements are true for multiple alleles? - How many alleles can be present in an organism for one gene? - How many copies of a recessive epistatic allele must be present for the expression of the hypostatic allele to be affected? - Which of the following statements about dominant epistasis are true? [Practise this topic for free](https://app.senecalearning.com/classroom/course/d0ce0c30-6417-11e8-8edc-d9cd1c890408/section/e649c44a-4ac6-4527-95dd-52257a642add/session) - Previous topic: [7.1.3 Linkage](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-3-linkage.md) - Next topic: [7.1.5 Chi-Squared Test](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-5-chi-squared-test.md) ## Biology: AQA A Level contents ### 1 Biological Molecules - 1.1 Monomers & Polymers - [1.1.1 Monomers & Polymers](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-1-1-monomers-and-polymers.md) - [1.1.2 Condensation & Hydrolysis Reactions](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-1-2-condensation-and-hydrolysis-reactions.md) - 1.2 Carbohydrates - [1.2.1 Structure of Carbohydrates](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-2-1-structure-of-carbohydrates.md) - [1.2.2 Types of Polysaccharides](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-2-2-types-of-polysaccharides.md) - [1.2.3 End of Topic Test - Monomers, Polymers and Carbs](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-2-3-end-of-topic-test-monomers-polymers-and-carbs.md) - [1.2.4 Exam-Style Question - Carbohydrates](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-2-4-exam-style-question-carbohydrates.md) - [1.2.5 A-A* (AO3/4) - Carbohydrates](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-2-5-a-a-ao34-carbohydrates.md) - 1.3 Lipids - [1.3.1 Triglycerides & Phospholipids](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-3-1-triglycerides-and-phospholipids.md) - [1.3.2 Types of Fatty Acids](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-3-2-types-of-fatty-acids.md) - [1.3.3 Testing for Lipids](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-3-3-testing-for-lipids.md) - [1.3.4 Exam-Style Question - Fats](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-3-4-exam-style-question-fats.md) - [1.3.5 A-A* (AO3/4) - Lipids](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-3-5-a-a-ao34-lipids.md) - 1.4 Proteins - [1.4.1 The Peptide Chain](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-1-the-peptide-chain.md) - [1.4.2 Investigating Proteins](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-2-investigating-proteins.md) - [1.4.3 Primary & Secondary Protein Structure](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-3-primary-and-secondary-protein-structure.md) - [1.4.4 Tertiary & Quaternary Protein Structure](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-4-tertiary-and-quaternary-protein-structure.md) - [1.4.5 Enzymes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-5-enzymes.md) - [1.4.6 Factors Affecting Enzyme Activity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-6-factors-affecting-enzyme-activity.md) - [1.4.7 Enzyme-Controlled Reactions](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-7-enzyme-controlled-reactions.md) - [1.4.8 End of Topic Test - Lipids & Proteins](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-8-end-of-topic-test-lipids-and-proteins.md) - [1.4.9 A-A* (AO3/4) - Enzymes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-9-a-a-ao34-enzymes.md) - [1.4.10 A-A* (AO3/4) - Proteins](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-10-a-a-ao34-proteins.md) - [1.4.11 Diagnostic Misconceptions - Enzyme Inhibitors](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-4-11-diagnostic-misconceptions-enzyme-inhibitors.md) - 1.5 Nucleic Acids - [1.5.1 DNA & RNA](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-5-1-dna-and-rna.md) - [1.5.2 Nucleotides](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-5-2-nucleotides.md) - [1.5.3 Polynucleotides](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-5-3-polynucleotides.md) - [1.5.4 DNA Replication](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-5-4-dna-replication.md) - [1.5.5 Exam-Style Question - Nucleic Acids](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-5-5-exam-style-question-nucleic-acids.md) - [1.5.6 A-A* (AO3/4) - Nucleic Acids](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-5-6-a-a-ao34-nucleic-acids.md) - 1.6 ATP - [1.6.1 Structure of ATP](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-6-1-structure-of-atp.md) - [1.6.2 Hydrolysis of ATP](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-6-2-hydrolysis-of-atp.md) - [1.6.3 Resynthesis of ATP](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-6-3-resynthesis-of-atp.md) - [1.6.4 End of Topic Test - Nucleic Acids & ATP](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-6-4-end-of-topic-test-nucleic-acids-and-atp.md) - 1.7 Water - [1.7.1 Importance of Water](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-7-1-importance-of-water.md) - [1.7.2 Structure of Water](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-7-2-structure-of-water.md) - [1.7.3 Properties of Water](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-7-3-properties-of-water.md) - [1.7.4 A-A* (AO3/4) - Water](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-7-4-a-a-ao34-water.md) - 1.8 Inorganic Ions - [1.8.1 Inorganic Ions](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-8-1-inorganic-ions.md) - [1.8.2 End of Topic Test - Water & Inorganic Ions](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/1-8-2-end-of-topic-test-water-and-inorganic-ions.md) ### 2 Cells - 2.1 Cell Structure - [2.1.1 Introduction to Cells](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-1-introduction-to-cells.md) - [2.1.2 Eukaryotic Cells & Organelles](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-2-eukaryotic-cells-and-organelles.md) - [2.1.3 Eukaryotic Cells & Organelles 2](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-3-eukaryotic-cells-and-organelles-2.md) - [2.1.4 Prokaryotes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-4-prokaryotes.md) - [2.1.5 A-A* (AO3/4) - Organelles](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-5-a-a-ao34-organelles.md) - [2.1.6 Methods of Studying Cells](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-6-methods-of-studying-cells.md) - [2.1.7 Microscopes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-7-microscopes.md) - [2.1.8 End of Topic Test - Cell Structure](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-8-end-of-topic-test-cell-structure.md) - [2.1.9 Exam-Style Question - Cells](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-9-exam-style-question-cells.md) - [2.1.10 A-A* (AO3/4) - Cells](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-1-10-a-a-ao34-cells.md) - 2.2 Mitosis & Cancer - [2.2.1 Mitosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-2-1-mitosis.md) - [2.2.2 Stages of Mitosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-2-2-stages-of-mitosis.md) - [2.2.3 Investigating Mitosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-2-3-investigating-mitosis.md) - [2.2.4 Cancer](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-2-4-cancer.md) - [2.2.5 A-A* (AO3/4) - The Cell Cycle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-2-5-a-a-ao34-the-cell-cycle.md) - 2.3 Transport Across Cell Membrane - [2.3.1 Cell Membrane Structure](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-1-cell-membrane-structure.md) - [2.3.2 A-A* (AO3/4) - Membrane Structure](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-2-a-a-ao34-membrane-structure.md) - [2.3.3 Diffusion](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-3-diffusion.md) - [2.3.4 Osmosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-4-osmosis.md) - [2.3.5 Active Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-5-active-transport.md) - [2.3.6 End of Topic Test - Mitosis, Cancer & Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-6-end-of-topic-test-mitosis-cancer-and-transport.md) - [2.3.7 Exam-Style Question - Membranes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-7-exam-style-question-membranes.md) - [2.3.8 A-A* (AO3/4) - Membranes & Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-8-a-a-ao34-membranes-and-transport.md) - [2.3.9 A-A*- Mitosis, Cancer & Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-3-9-a-a-mitosis-cancer-and-transport.md) - 2.4 Cell Recognition & the Immune System - [2.4.1 Immune System](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-1-immune-system.md) - [2.4.2 Phagocytosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-2-phagocytosis.md) - [2.4.3 T Lymphocytes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-3-t-lymphocytes.md) - [2.4.4 B Lymphocytes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-4-b-lymphocytes.md) - [2.4.5 Antibodies](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-5-antibodies.md) - [2.4.6 Primary & Secondary Response](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-6-primary-and-secondary-response.md) - [2.4.7 Vaccines](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-7-vaccines.md) - [2.4.8 HIV](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-8-hiv.md) - [2.4.9 Ethical Issues](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-9-ethical-issues.md) - [2.4.10 End of Topic Test - Immune System](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-10-end-of-topic-test-immune-system.md) - [2.4.11 Exam-Style Question - Immune System](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-11-exam-style-question-immune-system.md) - [2.4.12 A-A* (AO3/4) - Immune System](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-12-a-a-ao34-immune-system.md) - [2.4.13 Diagnostic Misconceptions - Humoral vs Cellular](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/2-4-13-diagnostic-misconceptions-humoral-vs-cellular.md) ### 3 Substance Exchange - 3.1 Surface Area to Volume Ratio - [3.1.1 Size & Surface Area](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-1-1-size-and-surface-area.md) - [3.1.2 A-A* (AO3/4) - Cell Size](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-1-2-a-a-ao34-cell-size.md) - 3.2 Gas Exchange - [3.2.1 Single-Celled Organisms](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-1-single-celled-organisms.md) - [3.2.2 Multicellular Organisms](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-2-multicellular-organisms.md) - [3.2.3 Control of Water Loss](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-3-control-of-water-loss.md) - [3.2.4 Human Gas Exchange](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-4-human-gas-exchange.md) - [3.2.5 Ventilation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-5-ventilation.md) - [3.2.6 Dissection](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-6-dissection.md) - [3.2.7 Measuring Gas Exchange](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-7-measuring-gas-exchange.md) - [3.2.8 Lung Disease](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-8-lung-disease.md) - [3.2.9 Lung Disease Data](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-9-lung-disease-data.md) - [3.2.10 End of Topic Test - Gas Exchange](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-10-end-of-topic-test-gas-exchange.md) - [3.2.11 A-A* (AO3/4) - Gas Exchange](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-2-11-a-a-ao34-gas-exchange.md) - 3.3 Digestion & Absorption - [3.3.1 Overview of Digestion](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-3-1-overview-of-digestion.md) - [3.3.2 Digestion in Mammals](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-3-2-digestion-in-mammals.md) - [3.3.3 Absorption](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-3-3-absorption.md) - [3.3.4 End of Topic Test - Substance Exchange & Digestion](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-3-4-end-of-topic-test-substance-exchange-and-digestion.md) - [3.3.5 A-A* (AO3/4) - Substance Ex & Digestion](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-3-5-a-a-ao34-substance-ex-and-digestion.md) - 3.4 Mass Transport - [3.4.1 Haemoglobin](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-1-haemoglobin.md) - [3.4.2 Oxygen Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-2-oxygen-transport.md) - [3.4.3 The Circulatory System](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-3-the-circulatory-system.md) - [3.4.4 The Heart](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-4-the-heart.md) - [3.4.5 Blood Vessels](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-5-blood-vessels.md) - [3.4.6 Cardiovascular Disease](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-6-cardiovascular-disease.md) - [3.4.7 Heart Dissection](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-7-heart-dissection.md) - [3.4.8 Xylem](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-8-xylem.md) - [3.4.9 Phloem](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-9-phloem.md) - [3.4.10 Investigating Plant Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-10-investigating-plant-transport.md) - [3.4.11 End of Topic Test - Mass Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-11-end-of-topic-test-mass-transport.md) - [3.4.12 A-A* (AO3/4) - Mass Transport](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-12-a-a-ao34-mass-transport.md) - [3.4.13 Diagnostic Misconceptions - Concentration Gradient](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-13-diagnostic-misconceptions-concentration-gradient.md) - [3.4.14 Diagnostic Misconceptions - Cardiac Cycle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-14-diagnostic-misconceptions-cardiac-cycle.md) - [3.4.15 Diagnostic Misconceptions - Carrying Capacity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-15-diagnostic-misconceptions-carrying-capacity.md) - [3.4.16 Diagnostic Misconceptions - Translocation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/3-4-16-diagnostic-misconceptions-translocation.md) ### 4 Genetic Information & Variation - 4.1 DNA, Genes & Chromosomes - [4.1.1 DNA](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-1-1-dna.md) - [4.1.2 Genes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-1-2-genes.md) - [4.1.3 Non-Coding Genes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-1-3-non-coding-genes.md) - [4.1.4 The Genetic Code](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-1-4-the-genetic-code.md) - [4.1.5 A-A* (AO3/4) - DNA](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-1-5-a-a-ao34-dna.md) - 4.2 DNA & Protein Synthesis - [4.2.1 Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-1-protein-synthesis.md) - [4.2.2 Transcription & Translation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-2-transcription-and-translation.md) - [4.2.3 End of Topic Test - DNA, Genes & Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-3-end-of-topic-test-dna-genes-and-protein-synthesis.md) - [4.2.4 Exam-Style Question - Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-4-exam-style-question-protein-synthesis.md) - [4.2.5 A-A* (AO3/4) - Coronavirus Translation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-5-a-a-ao34-coronavirus-translation.md) - [4.2.6 A-A* (AO3/4) - Transcription](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-6-a-a-ao34-transcription.md) - [4.2.7 A-A* (AO3/4) - Translation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-2-7-a-a-ao34-translation.md) - 4.3 Mutations & Meiosis - [4.3.1 Mutations](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-1-mutations.md) - [4.3.2 Meiosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-2-meiosis.md) - [4.3.3 A-A* (AO3/4) - Meiosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-3-a-a-ao34-meiosis.md) - [4.3.4 Meiosis vs Mitosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-4-meiosis-vs-mitosis.md) - [4.3.5 End of Topic Test - Mutations, Meiosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-5-end-of-topic-test-mutations-meiosis.md) - [4.3.6 A-A* (AO3/4) - DNA,Genes, CellDiv & ProtSynth](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-6-a-a-ao34-dnagenes-celldiv-and-protsynth.md) - [4.3.7 Diagnostic Misconceptions - Meiosis vs Mitosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-3-7-diagnostic-misconceptions-meiosis-vs-mitosis.md) - 4.4 Genetic Diversity & Adaptation - [4.4.1 Genetic Diversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-1-genetic-diversity.md) - [4.4.2 Natural Selection](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-2-natural-selection.md) - [4.4.3 A-A* (AO3/4) - Natural Selection](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-3-a-a-ao34-natural-selection.md) - [4.4.4 Adaptations](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-4-adaptations.md) - [4.4.5 Investigating Natural Selection](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-5-investigating-natural-selection.md) - [4.4.6 End of Topic Test - Genetic Diversity & Adaptation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-6-end-of-topic-test-genetic-diversity-and-adaptation.md) - [4.4.7 A-A* (AO3/4) - Genetic Diversity & Adaptation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-4-7-a-a-ao34-genetic-diversity-and-adaptation.md) - 4.5 Species & Taxonomy - [4.5.1 Courtship Behaviour](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-5-1-courtship-behaviour.md) - [4.5.2 Phylogeny](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-5-2-phylogeny.md) - [4.5.3 Classification](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-5-3-classification.md) - [4.5.4 DNA Technology](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-5-4-dna-technology.md) - [4.5.5 A-A* (AO3/4) - Species & Taxonomy](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-5-5-a-a-ao34-species-and-taxonomy.md) - 4.6 Biodiversity Within a Community - [4.6.1 Biodiversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-6-1-biodiversity.md) - [4.6.2 Index of diversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-6-2-index-of-diversity.md) - [4.6.3 Agriculture](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-6-3-agriculture.md) - [4.6.4 End of Topic Test - Species,Taxonomy& Biodiversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-6-4-end-of-topic-test-speciestaxonomyand-biodiversity.md) - [4.6.5 A-A* (AO3/4) - Species,Taxon&Biodiversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-6-5-a-a-ao34-speciestaxonandbiodiversity.md) - 4.7 Investigating Diversity - [4.7.1 Genetic Diversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-7-1-genetic-diversity.md) - [4.7.2 Quantitative Investigation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/4-7-2-quantitative-investigation.md) ### 5 Energy Transfers (A2 only) - 5.1 Photosynthesis - [5.1.1 Overview of Photosynthesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-1-overview-of-photosynthesis.md) - [5.1.2 Photoionisation of Chlorophyll](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-2-photoionisation-of-chlorophyll.md) - [5.1.3 Production of ATP & Reduced NADP](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-3-production-of-atp-and-reduced-nadp.md) - [5.1.4 Cyclic Photophosphorylation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-4-cyclic-photophosphorylation.md) - [5.1.5 Light-Independent Reaction](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-5-light-independent-reaction.md) - [5.1.6 A-A* (AO3/4) - Photosynthesis Reactions](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-6-a-a-ao34-photosynthesis-reactions.md) - [5.1.7 Limiting Factors](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-7-limiting-factors.md) - [5.1.8 Photosynthesis Experiments](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-8-photosynthesis-experiments.md) - [5.1.9 End of Topic Test - Photosynthesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-9-end-of-topic-test-photosynthesis.md) - [5.1.10 A-A* (AO3/4) - Photosynthesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-1-10-a-a-ao34-photosynthesis.md) - 5.2 Respiration - [5.2.1 Overview of Respiration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-1-overview-of-respiration.md) - [5.2.2 Anaerobic Respiration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-2-anaerobic-respiration.md) - [5.2.3 A-A* (AO3/4) - Anaerobic Respiration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-3-a-a-ao34-anaerobic-respiration.md) - [5.2.4 The Link Reaction](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-4-the-link-reaction.md) - [5.2.5 The Krebs Cycle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-5-the-krebs-cycle.md) - [5.2.6 Oxidative Phosphorylation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-6-oxidative-phosphorylation.md) - [5.2.7 Respiration Experiments](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-7-respiration-experiments.md) - [5.2.8 End of Topic Test - Respiration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-8-end-of-topic-test-respiration.md) - [5.2.9 A-A* (AO3/4) - Respiration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-9-a-a-ao34-respiration.md) - [5.2.10 Diagnostic Misconceptions - Aerobic vs Anaerobic](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-2-10-diagnostic-misconceptions-aerobic-vs-anaerobic.md) - 5.3 Energy & Ecosystems - [5.3.1 Biomass](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-3-1-biomass.md) - [5.3.2 Production & Productivity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-3-2-production-and-productivity.md) - [5.3.3 Agricultural Practices](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-3-3-agricultural-practices.md) - 5.4 Nutrient Cycles - [5.4.1 Nitrogen Cycle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-4-1-nitrogen-cycle.md) - [5.4.2 Phosphorous Cycle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-4-2-phosphorous-cycle.md) - [5.4.3 Fertilisers & Eutrophication](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-4-3-fertilisers-and-eutrophication.md) - [5.4.4 End of Topic Test - Nutrient Cycles](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-4-4-end-of-topic-test-nutrient-cycles.md) - [5.4.5 A-A* (AO3/4) - Energy,Ecosystems&NutrientCycles](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/5-4-5-a-a-ao34-energyecosystemsandnutrientcycles.md) ### 6 Responding to Change (A2 only) - 6.1 Nervous Communication - [6.1.1 Survival](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-1-survival.md) - [6.1.2 Plant Responses](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-2-plant-responses.md) - [6.1.3 Animal Responses](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-3-animal-responses.md) - [6.1.4 Reflexes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-4-reflexes.md) - [6.1.5 End of Topic Test - Reflexes, Responses & Survival](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-5-end-of-topic-test-reflexes-responses-and-survival.md) - [6.1.6 Receptors](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-6-receptors.md) - [6.1.7 The Human Retina](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-7-the-human-retina.md) - [6.1.8 Control of Heart Rate](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-8-control-of-heart-rate.md) - [6.1.9 End of Topic Test - Receptors, Retina & Heart Rate](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-1-9-end-of-topic-test-receptors-retina-and-heart-rate.md) - 6.2 Nervous Coordination - [6.2.1 Neurones](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-1-neurones.md) - [6.2.2 Action Potentials](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-2-action-potentials.md) - [6.2.3 Speed of Transmission](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-3-speed-of-transmission.md) - [6.2.4 End of Topic Test - Neurones & Action Potentials](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-4-end-of-topic-test-neurones-and-action-potentials.md) - [6.2.5 Synapses](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-5-synapses.md) - [6.2.6 Types of Synapse](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-6-types-of-synapse.md) - [6.2.7 Medical Application](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-7-medical-application.md) - [6.2.8 End of Topic Test - Synapses](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-8-end-of-topic-test-synapses.md) - [6.2.9 A-A* (AO3/4) - Nervous Comm&Coord](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-2-9-a-a-ao34-nervous-commandcoord.md) - 6.3 Muscle Contraction - [6.3.1 Skeletal Muscle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-3-1-skeletal-muscle.md) - [6.3.2 Sliding Filament Theory](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-3-2-sliding-filament-theory.md) - [6.3.3 Contraction](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-3-3-contraction.md) - [6.3.4 Slow & Fast Twitch Fibres](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-3-4-slow-and-fast-twitch-fibres.md) - [6.3.5 End of Topic Test - Muscles](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-3-5-end-of-topic-test-muscles.md) - [6.3.6 A-A* (AO3/4) - Muscle Contraction](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-3-6-a-a-ao34-muscle-contraction.md) - 6.4 Homeostasis - [6.4.1 Overview of Homeostasis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-1-overview-of-homeostasis.md) - [6.4.2 Blood Glucose Concentration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-2-blood-glucose-concentration.md) - [6.4.3 Controlling Blood Glucose Concentration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-3-controlling-blood-glucose-concentration.md) - [6.4.4 End of Topic Test - Blood Glucose](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-4-end-of-topic-test-blood-glucose.md) - [6.4.5 Primary & Secondary Messengers](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-5-primary-and-secondary-messengers.md) - [6.4.6 Diabetes Mellitus](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-6-diabetes-mellitus.md) - [6.4.7 Measuring Glucose Concentration](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-7-measuring-glucose-concentration.md) - [6.4.8 Osmoregulation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-8-osmoregulation.md) - [6.4.9 Controlling Blood Water Potential](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-9-controlling-blood-water-potential.md) - [6.4.10 ADH](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-10-adh.md) - [6.4.11 End of Topic Test - Diabetes & Osmoregulation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-11-end-of-topic-test-diabetes-and-osmoregulation.md) - [6.4.12 A-A* (AO3/4) - Homeostasis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-12-a-a-ao34-homeostasis.md) - [6.4.13 Diagnostic Misconceptions - Effect of ADH](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/6-4-13-diagnostic-misconceptions-effect-of-adh.md) ### 7 Genetics & Ecosystems (A2 only) - 7.1 Genetics - [7.1.1 Key Terms in Genetics](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-1-key-terms-in-genetics.md) - [7.1.2 Inheritance](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-2-inheritance.md) - [7.1.3 Linkage](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-3-linkage.md) - [7.1.4 Multiple Alleles & Epistasis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-4-multiple-alleles-and-epistasis.md) - [7.1.5 Chi-Squared Test](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-5-chi-squared-test.md) - [7.1.6 End of Topic Test - Genetics](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-6-end-of-topic-test-genetics.md) - [7.1.7 A-A* (AO3/4) - Genetics](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-7-a-a-ao34-genetics.md) - [7.1.8 Diagnostic Misconceptions - Dihybrid Inheritance](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-8-diagnostic-misconceptions-dihybrid-inheritance.md) - [7.1.9 Diagnostic Misconceptions - Sex Linkage](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-1-9-diagnostic-misconceptions-sex-linkage.md) - 7.2 Populations - [7.2.1 Populations](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-2-1-populations.md) - [7.2.2 Hardy-Weinberg Principle](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-2-2-hardy-weinberg-principle.md) - 7.3 Evolution - [7.3.1 Variation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-1-variation.md) - [7.3.2 Natural Selection & Evolution](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-2-natural-selection-and-evolution.md) - [7.3.3 End of Topic Test - Populations & Evolution](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-3-end-of-topic-test-populations-and-evolution.md) - [7.3.4 Types of Selection](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-4-types-of-selection.md) - [7.3.5 Types of Selection Summary](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-5-types-of-selection-summary.md) - [7.3.6 Overview of Speciation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-6-overview-of-speciation.md) - [7.3.7 Causes of Speciation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-7-causes-of-speciation.md) - [7.3.8 Diversity](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-8-diversity.md) - [7.3.9 End of Topic Test - Selection & Speciation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-9-end-of-topic-test-selection-and-speciation.md) - [7.3.10 A-A* (AO3/4) - Populations & Evolution](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-10-a-a-ao34-populations-and-evolution.md) - [7.3.11 Diagnostic Misconceptions - Types of Speciation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-3-11-diagnostic-misconceptions-types-of-speciation.md) - 7.4 Populations in Ecosystems - [7.4.1 Overview of Ecosystems](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-1-overview-of-ecosystems.md) - [7.4.2 Niche](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-2-niche.md) - [7.4.3 Population Size](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-3-population-size.md) - [7.4.4 Investigating Population Size](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-4-investigating-population-size.md) - [7.4.5 End of Topic Test - Ecosystems & Population Size](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-5-end-of-topic-test-ecosystems-and-population-size.md) - [7.4.6 Succession](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-6-succession.md) - [7.4.7 Conservation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-7-conservation.md) - [7.4.8 End of Topic Test - Succession & Conservation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-8-end-of-topic-test-succession-and-conservation.md) - [7.4.9 A-A* (AO3/4) - Ecosystems](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/7-4-9-a-a-ao34-ecosystems.md) ### 8 The Control of Gene Expression (A2 only) - 8.1 Mutation - [8.1.1 Mutations](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-1-1-mutations.md) - [8.1.2 Effects of Mutations](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-1-2-effects-of-mutations.md) - [8.1.3 Causes of Mutations](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-1-3-causes-of-mutations.md) - [8.1.4 Diagnostic Misconceptions - Gene Expression](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-1-4-diagnostic-misconceptions-gene-expression.md) - 8.2 Gene Expression - [8.2.1 Stem Cells](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-1-stem-cells.md) - [8.2.2 Stem Cells in Disease](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-2-stem-cells-in-disease.md) - [8.2.3 End of Topic Test - Mutation & Gene Epression](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-3-end-of-topic-test-mutation-and-gene-epression.md) - [8.2.4 A-A* (AO3/4) - Mutation & Stem Cells](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-4-a-a-ao34-mutation-and-stem-cells.md) - [8.2.5 Regulating Transcription](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-5-regulating-transcription.md) - [8.2.6 Epigenetics](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-6-epigenetics.md) - [8.2.7 Epigenetics & Disease](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-7-epigenetics-and-disease.md) - [8.2.8 Regulating Translation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-8-regulating-translation.md) - [8.2.9 Experimental Data](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-9-experimental-data.md) - [8.2.10 End of Topic Test - Transcription & Translation](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-10-end-of-topic-test-transcription-and-translation.md) - [8.2.11 Tumours](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-11-tumours.md) - [8.2.12 Correlations & Causes](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-12-correlations-and-causes.md) - [8.2.13 Prevention & Treatment](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-13-prevention-and-treatment.md) - [8.2.14 End of Topic Test - Cancer](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-14-end-of-topic-test-cancer.md) - [8.2.15 A-A* (AO3/4) - Gene Expression & Cancer](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-2-15-a-a-ao34-gene-expression-and-cancer.md) - 8.3 Genome Projects - [8.3.1 Using Genome Projects](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-3-1-using-genome-projects.md) - 8.4 Gene Technology - [8.4.1 Recombinant DNA](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-1-recombinant-dna.md) - [8.4.2 Producing Fragments](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-2-producing-fragments.md) - [8.4.3 Amplification](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-3-amplification.md) - [8.4.4 End of Topic Test - Genome Project & Amplification](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-4-end-of-topic-test-genome-project-and-amplification.md) - [8.4.5 Using Recombinant DNA](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-5-using-recombinant-dna.md) - [8.4.6 Medical Diagnosis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-6-medical-diagnosis.md) - [8.4.7 Genetic Fingerprinting](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-7-genetic-fingerprinting.md) - [8.4.8 End of Topic Test - Gene Technologies](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-8-end-of-topic-test-gene-technologies.md) - [8.4.9 A-A* (AO3/4) - Gene Technology](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/8-4-9-a-a-ao34-gene-technology.md) ### 9 Mathematical Skills - 9.1 Mathematical Skills - [9.1.1 Diagnostic Misconceptions - Converting Units](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/9-1-1-diagnostic-misconceptions-converting-units.md) - [9.1.2 Diagnostic Misconceptions - Correct Hypothesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/9-1-2-diagnostic-misconceptions-correct-hypothesis.md) - [9.1.3 Diagnostic Misconceptions - Interpret Hypothesis](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/9-1-3-diagnostic-misconceptions-interpret-hypothesis.md) - [9.1.4 Diagnostic Misconceptions - Calculate Uncertainty](https://senecalearning.com/en-gb/revision-notes/a-level/biology/aqa/9-1-4-diagnostic-misconceptions-calculate-uncertainty.md)