Key term
CCEA A-Level Biology 1010
Biological Molecules
Topic overviewWater as a solventInorganic ions and their rolesMonosaccharides and the glycosidic bondDisaccharides and polysaccharidesLipids, triglycerides and phospholipidsAmino acids and protein structureProtein shape, conjugated proteins and prionsNucleic acids: nucleotides, DNA and RNADNA replication and the Meselson–Stahl experimentBiochemical tests and paper chromatography
Enzymes
Topic overviewEnzymes as globular proteins and the active siteSpecificity, cofactors and coenzymesActivation energy and models of enzyme actionThe effect of temperature and pHThe effect of substrate and enzyme concentrationCompetitive and non-competitive inhibitionEnzymes as biomarkers of disease and inhibitors as drugsImmobilised enzymes and biosensors
Viruses and Cell Structure
Topic overviewBacteriophage and HIV structureViral replication in host cellsProkaryotic and eukaryotic cells comparedMembrane structure: the fluid mosaic modelFunctions of membrane componentsMitochondria and chloroplastsRibosomes, endoplasmic reticulum, Golgi apparatus and lysosomesThe nucleus, the cytoskeleton and plasmodesmataPlant, fungal and animal cellsMicroscopy, cell measurement and cell fractionation
Cell Physiology and Transport
Continuity of Cells
Topic overviewThe cell cycle: interphase and the gap phasesControl points in the cell cycle and cancerChromosome structure, haploidy and diploidyMitosis: the events of the four stagesCytokinesis and the significance of mitosisAnticancer drugs and the cell cycleMeiosis I and the first divisionMeiosis II and the significance of meiosisPreparing and examining slides of cell division
Tissues and Organs
Exchange Surfaces and Gas Exchange
Topic overviewSurface area, volume and the surface area to volume ratioFeatures of efficient exchange surfacesThe need for mass transport systemsFick's law and the rate of gas exchangeGas exchange in plants and the compensation pointGas exchange at the alveolusThe respiratory tree and the mechanism of ventilationThe effects of smoking on the breathing systemUsing a respirometer to measure gas exchange
Transport in Plants
Topic overviewEpidermis, endodermis and the tissues of the rootXylem vessels and their lignification patternsPhloem: sieve-tube elements and companion cellsWater and mineral ion uptake by root hairsThe apoplast and symplast pathwaysTranspiration and the factors affecting its rateCohesion-tension theory and the transpiration streamTranslocation of organic solutes in the phloemXerophytes and hydrophytes
The Circulatory System in Mammals
Topic overviewDouble circulation and the major blood vesselsThe structure and function of arteries, veins and capillariesAtherosclerosis, atheroma and the investigation of blood vesselsThe structure of the mammalian heartThe cardiac cycle and the operation of the valvesMyogenic stimulation and the electrocardiogramBlood cells and the stained blood filmPlasma, tissue fluid and blood clottingHaemoglobin and the oxygen dissociation curveThe Bohr effect, myoglobin and altitude
Adaptation and Biodiversity
Topic overviewAdaptation and the ways organisms meet environmental challengesEcological factors and the ecological nicheSampling procedures and sampling devicesEstimating abundance, density, frequency and percentage coverThe biochemical basis of life and the levels of biodiversityMeasuring species diversity with Simpson's indexHandling data: averages, spread and the t-testTaxonomy, nomenclature and the binomial systemThe concept of a speciesThe taxonomic hierarchy from genus to kingdomPhylogenetic taxonomy and molecular evidenceThe five kingdom system: prokaryotae, protoctista and fungiPlantae, animalia and alternative classification systems
Human Impact on Biodiversity
Topic overviewMonoculture, polyculture and intensive agricultureCrop rotation and hedgerow conservationPredator strips, pesticides and integrated pest managementOrganic pollution of waterways by slurry and silage effluentEutrophication and fertiliser run-offBiological oxygen demand and reducing aquatic pollutionConservation initiatives and habitat protectionGlobal warming, climate change and biodiversity
Homeostasis and Excretion
Topic overviewPrinciples of homeostasis and negative feedbackExcretion, osmoregulation and nitrogenous wasteGross structure of the kidney and the urinary systemStructure of the nephron and its blood supplyEpithelia of the nephron and their adaptationsThe glomerular filterUltrafiltration and the forces that drive itSelective reabsorption in the proximal convoluted tubuleThe loop of Henlé and the medullary salt gradientADH, osmoreceptors and the control of water balance
Immunity
Topic overviewNatural barriers to infectionAntigens, antibodies and the antigen–antibody reactionAntibody-mediated immunity and B-lymphocytesCell-mediated immunity and T-lymphocytesActive immunity, passive immunity and vaccinationTransplant rejection and immunosuppressionBlood group polymorphism and the rhesus factorTransfusion compatibility and its consequencesAntibiotic resistance and the search for new antimicrobialsELISA and the detection of disease biomarkers
Co-Ordination and Control
Topic overviewPhytochromes and the control of floweringPlant growth substances and stem elongationThe structure of a neuroneResting potential, threshold and the action potentialImpulse propagation and the speed of conductionSynapse structure and chemical transmissionExcitatory and inhibitory post-synaptic potentialsGross structure of the eye and accommodationThe retina, rods and conesSkeletal muscle and the sliding filament theory
Populations and Communities
Topic overviewPopulation growth curves, carrying capacity and environmental resistancer-selected and K-selected speciesInteractions between populationsBiological control of pest speciesPopulation dynamics and changes in population sizeEstimating population size in the field and the laboratoryCommunities and ecosystemsSuccession and climax communities
Ecological Energetics and Nutrient Cycling
Topic overviewFood chains, food webs and detritus food chainsTrophic levels, gross and net primary productionEcological pyramids and their usefulnessEnergy transfer efficiency between trophic levelsWhy energy is lost at each trophic levelImplications for agriculture and intensive farmingThe carbon cycleThe nitrogen cycle and the role of bacteria
Respiration
Topic overviewATP and the ATP/ADP cycleGlycolysisThe mitochondrion and the sites of aerobic respirationThe link reaction and the Krebs cycleThe electron transport chain and oxidative phosphorylationATP yield from one molecule of glucoseAnaerobic respiration in animals, plants and fungiAerobic and anaerobic respiration compared, and oxygen debtRespiratory quotient and measuring respiration
Photosynthesis
Topic overviewChloroplast structure and the sites of photosynthesisPhotosynthetic pigments and paper chromatographyAbsorption spectra and action spectraPhotosystems, photoactivation and the Z-schemePhotolysis of water, reduced NADP and redox indicatorsCarbon dioxide fixation and rubiscoReduction of glycerate phosphate and regeneration of ribulose bisphosphateLimiting factors, the compensation point and measuring photosynthesis
DNA as the Genetic Code
Topic overviewGenes and the nature of the genetic codeExons, introns and RNA splicingComparing DNA and RNATranscription and RNA polymeraseTransfer RNA, ribosomes and the sites of translationTranslation and polypeptide synthesisOne gene, one polypeptide and the control of the phenotypeEpigenetics, methylation and histone modification
Gene Technology
Topic overviewThe polymerase chain reactionDNA probes and genetic markersMicroarrays, pharmacogenetics and personalised medicineGenetic fingerprinting and gel electrophoresisThe stages of gene transferGenetically modified microorganismsTransgenic animals and plantsGene therapyGenome sequencing and the Human Genome ProjectGene inactivation and knockout organismsSocial, ethical and ecological issues of gene technology
Genes and Patterns of Inheritance
Topic overviewGenotype, phenotype and the environmentChromosomes, genes and allelesMonohybrid inheritance and Mendel's first lawCodominance, multiple alleles and lethal allelesTest crossesDihybrid inheritance and Mendel's second lawAutosomes, sex chromosomes and sex determinationGene interaction and epistasisPolygenic inheritance and continuous variationThe chi-squared test
Population Genetics and Evolution
Evolutionary Trends in Plants
Genes and Patterns of Inheritance
- 10 subtopics
- 30 things to know
- Unit A2 2
What Genes and Patterns of Inheritance covers
Genes and Patterns of Inheritance is examined in Unit A2 2, Biochemistry, Genetics and Evolutionary Trends, and drawn on again in Unit A2 3, the practical skills examination. It covers genotype, phenotype and the environment, chromosomes, genes and alleles, monohybrid inheritance and Mendel's first law, codominance, multiple alleles and lethal alleles, test crosses, dihybrid inheritance and Mendel's second law, autosomes, sex chromosomes and sex determination, gene interaction and epistasis and polygenic inheritance and continuous variation.
Where it is assessed
Unit A2 2
Biochemistry, Genetics and Evolutionary Trends, and again in Unit A2 3, Practical Skills in Biology.
Check the CCEA specification ↗The 10 subtopics
Each one has its own page.
- Genotype, phenotype and the environmentTerm genotype, term phenotype and environment affecting a phenotype in a plant.Open →
- Chromosomes, genes and allelesRecall questions on what defines a gene, the locus, homologous chromosomes and how the two alleles at a locus can differ, the meaning of diploid and haploid, and how a new allele arises.Open →
- Monohybrid inheritance and Mendel's first lawMonohybrid inheritance, mendel's first law and four elements a genetic diagram must show.Open →
- Codominance, multiple alleles and lethal allelesPhenotypic ratio from crossing two pink codominant heterozygotes, multiple alleles and three alleles of the human ABO blood group gene.Open →
- Test crossesTest cross and back cross.Open →
- Dihybrid inheritance and Mendel's second lawDihybrid inheritance, mendel's second law and phenotypic ratio from crossing two individuals heterozygous at two loci.Open →
- Autosomes, sex chromosomes and sex determinationExpected ratio of male to female offspring in mammals and sex-linked characteristic.Open →
- Gene interaction and epistasisGene interaction, epistatic gene and hypostatic gene.Open →
- Polygenic inheritance and continuous variationPolygenic inheritance, additive effect of polygenes and balanced conclusion about the causes of continuous variation.Open →
- The chi-squared testThe chi-squared formula, expected numbers and degrees of freedom, null hypotheses, and worked tests of monohybrid and dihybrid ratios read against the critical value at p = 0.05.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
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Why is a 1 : 1 ratio the signature of a heterozygote in a test cross?
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Give a biochemical explanation of recessive epistasis.
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What is a locus?
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What is monohybrid inheritance?
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What is codominance?
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What is dihybrid inheritance?
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What is an autosome?
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What is polygenic inheritance?
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Define the term genotype.
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What is an allele?
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State Mendel's first law.
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In a codominant flower colour gene, one allele gives red and the other white. What colour is the heterozygote?
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What is a test cross?
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State Mendel's second law.
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How many pairs of autosomes does a human cell contain?
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What is meant by gene interaction?
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What are polygenes?
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Define the term phenotype.
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What are homologous chromosomes?
Process
Which stage of meiosis brings about segregation?
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State the phenotypic ratio from crossing two pink codominant heterozygotes.
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What result shows the tested individual was homozygous dominant?
Process
Which stage of meiosis brings about independent assortment?
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State the sex chromosome constitution of a human female and a human male.
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What is the epistatic gene?
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What is meant by the additive effect of polygenes?
Process
Why must raw counts rather than percentages be used in a chi-squared test?
Process
Why is the chi-squared test unreliable when expected numbers are very small?
Process
A cross gives 290 tall and 110 dwarf where 3:1 is expected. Is the difference significant?
Take Genes and Patterns of Inheritance further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Homozygous vs Heterozygous
Homozygous: the two alleles at a locus are identical. Heterozygous: meaning they differ.
Hemizygous vs Homozygous
Hemizygous: only a single allele of the gene is present at all. Homozygous: meaning two identical alleles are present.
Questions from this topic
Each one with the model answer underneath.
- 1
Define the term genotype.
Model answer
The genetic constitution of an organism, meaning the alleles it carries.
- 2
Define the term phenotype.
Model answer
The observable characteristics of an organism, produced by the interaction of its genotype with the environment.
- 3
Why is the phenotype not determined by the genotype alone?
Model answer
The environment affects how the genotype is expressed, so two organisms with the same alleles can differ in appearance.
- 4
Give an example of the environment affecting a phenotype in a plant.
Model answer
A plant with the genotype for tallness stays short if it is grown in poor soil or in low light.
- 5
Give an example of the environment affecting a phenotype in an animal.
Model answer
The coat colour of a Himalayan rabbit is dark only on the cooler extremities, because the enzyme producing the pigment is inactivated at higher temperature.
- 6
What does homozygous mean?
Model answer
Carrying two identical alleles of a gene at the same locus.
What is inside Levo
Six ways to work the same material.
Genes and Patterns of Inheritance revision questions
- What does Genes and Patterns of Inheritance cover in CCEA A-Level Biology?
- 10 subtopics: genotype, phenotype and the environment, chromosomes, genes and alleles, monohybrid inheritance and mendel's first law, codominance, multiple alleles and lethal alleles, test crosses, dihybrid inheritance and mendel's second law, autosomes, sex chromosomes and sex determination, gene interaction and epistasis, polygenic inheritance and continuous variation and the chi-squared test. Each one has its own page with questions and model answers.
- How is Genes and Patterns of Inheritance organised?
- By the CCEA 1010 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Genes and Patterns of Inheritance, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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