Key term
OCR GCSE Biology A J247
Cell Level Systems
Topic overviewMicroscopy, and sub-cellular structuresDNA structure: polymer, double helix and nucleotidesProtein synthesis and the triplet codeEnzyme action, and investigating enzymesCellular respiration as an exothermic processAerobic and anaerobic respiration comparedSynthesis and breakdown of carbohydrates, proteins and lipidsPhotosynthesis: producers and the processPhotosynthesis as endothermic, and investigating itLimiting factors in photosynthesis
Community Level Systems
Genes, Inheritance and Selection
Topic overviewGenetic terms, and the genomeGenome, environment and mutationsHow genetic variants influence phenotypeAsexual and sexual reproduction comparedHaploid, diploid and meiosisSingle gene inheritance and Punnett squaresSex determination, multiple genes and Mendel's workVariation within a population, and classificationNatural selection and evolutionEvidence for evolution, and the work of Darwin and Wallace
Global Challenges
Topic overviewField investigations, and human impact on ecosystemsMaintaining biodiversity, and evidence for environmental changeFood security, agricultural and biotechnological solutionsSelective breeding and genetic engineeringHealth, disease, and types of diseaseInteractions between diseases, and how they spreadReducing the spread of disease, and named examplesPhysical and chemical plant defencesDetecting plant disease; white blood cells and plateletsNon-specific defences and the immune systemMonoclonal antibodies and their usesVaccines, medicines and aseptic techniqueDeveloping new medicines, and non-communicable diseaseTreating cardiovascular disease, and lifestyle factorsCancer, and the use of stem cells in medicineGene technology in medicine, and the human genome
Organism Level Systems
Topic overviewThe nervous system and coordinated responsesThe reflex arcThe eye and its common defectsThe structure and function of the brainInvestigating and treating the brainHormonal coordination, thyroxine and adrenalineHormones in reproduction and the menstrual cycleContraception and treating infertilityPlant hormones and their commercial usesHomeostasis, and the skin in temperature controlInsulin and glucagon in blood sugar controlType 1 and type 2 diabetesOsmotic changes in body fluids, and the kidneysThe kidney tubule and the effect of ADHResponding to temperature and osmotic challenges
Scaling Up
Topic overviewDiffusion, osmosis and active transportMitosis, the cell cycle and cell differentiationStem cells in animals and meristems in plantsSurface area to volume ratio and exchange surfacesThe circulatory system, the heart and blood vesselsRed blood cells and plasmaRoot hair cells, transpiration and translocationXylem and phloemFactors affecting water uptake, and the potometer
Genes, Inheritance and Selection
Genome, environment and mutations
- 3 things to know
- Paper 4
Overview
How the genome and the environment together determine phenotype, discontinuous and continuous variation with examples such as eye colour and height and how each is usually controlled, mutations as the source of all genetic variants, the three possible effects of a mutation on the phenotype and which is rarest, why most have no effect, and why not all mutations are harmful.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What is continuous variation?
Key term
Give two human characteristics that show continuous variation.
Questions from this subtopic
Each one with the model answer underneath.
- 1
What two things together determine the phenotype of an organism?
Model answer
Its genome, and the interaction of that genome with the environment.
- 2
What is discontinuous variation?
Model answer
Variation in which individuals fall into a small number of distinct categories with no values in between.
- 3
Give an example of a human characteristic that shows discontinuous variation.
Model answer
Eye colour.
- 4
What is continuous variation?
Model answer
Variation in which individuals can take any value across a range, with no distinct categories.
- 5
Give two human characteristics that show continuous variation.
Model answer
Height and weight.
- 6
Explain why height in humans shows continuous variation.
Model answer
It is controlled by several genes acting together, and it is also affected by environmental factors such as diet.
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