Biology_A-level_Aqa
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1-biological-molecules
1-1-biological-molecules-carbohydrates11 主题-
1-1-1-biological-molecules-key-terms
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1-1-2-biological-molecules-reactions
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1-1-3-monosaccharides
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1-1-4-glucose
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1-1-5-the-glycosidic-bond
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1-1-6-chromatography-monosaccharides
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1-1-7-disaccharides
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1-1-8-starch-and-glycogen
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1-1-9-cellulose
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1-1-10-biochemical-tests-sugars-and-starch
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1-1-11-finding-the-concentration-of-glucose
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1-1-1-biological-molecules-key-terms
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1-2-biological-molecules-lipids3 主题
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1-3-biological-molecules-proteins5 主题
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1-4-proteins-enzymes12 主题
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1-4-1-many-proteins-are-enzymes
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1-4-2-enzyme-specificity
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1-4-3-how-enzymes-work
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1-4-4-required-practical-measuring-enzyme-activity
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1-4-5-drawing-a-graph-for-enzyme-rate-experiments
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1-4-6-using-a-tangent-to-find-initial-rate-of-reaction
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1-4-7-limiting-factors-affecting-enzymes-temperature
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1-4-8-limiting-factors-affecting-enzymes-ph
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1-4-10-limiting-factors-affecting-enzymes-enzyme-concentration
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1-4-11-limiting-factors-affecting-enzymes-substrate-concentration
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1-4-12-limiting-factors-affecting-enzymes-inhibitors
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1-4-14-control-of-variables-and-uncertainty
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1-4-1-many-proteins-are-enzymes
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1-5-nucleic-acids-structure-and-dna-replication8 主题
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1-5-2-nucleotide-structure-and-the-phosphodiester-bond
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1-5-3-dna-structure-and-function
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1-5-4-rna-structure-and-function
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1-5-5-ribosomes
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1-5-6-the-origins-of-research-on-the-genetic-code
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1-5-8-the-process-of-semi-conservative-replication
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1-5-9-calculating-the-frequency-of-nucleotide-bases
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1-5-10-the-watson-crick-model
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1-5-2-nucleotide-structure-and-the-phosphodiester-bond
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1-6-atp-water-and-inorganic-ions4 主题
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2-cell-structure2-1-cell-structure7 主题
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2-2-the-microscope-in-cell-studies4 主题
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2-3-cell-division-in-eukaryotic-and-prokaryotic-cells8 主题
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2-4-cell-membranes-and-transport7 主题
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2-5-cell-recognition-and-the-immune-system7 主题
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2-6-vaccines-disease-and-monoclonal-antibodies6 主题
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3-exchange-and-transport3-1-adaptations-for-gas-exchange6 主题
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3-2-human-gas-exchange10 主题
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3-2-1-the-human-gas-exchange-system
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3-2-2-dissecting-the-gas-exchange-system
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3-2-3-microscopy-and-gas-exchange-surfaces
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3-2-4-investigating-gas-exchange
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3-2-5-the-alveolar-epithelium
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3-2-6-ventilation-and-gas-exchange
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3-2-8-the-effects-of-lung-disease
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3-2-9-pollution-and-smoking-data
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3-2-10-risk-factor-data
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3-2-11-correlations-and-causal-relationships
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3-2-1-the-human-gas-exchange-system
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3-3-digestion-and-absorption5 主题
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3-4-mass-transport-in-animals6 主题
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3-5-the-circulatory-system-in-animals8 主题
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3-6-mass-transport-in-plants6 主题
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4-genetics-variation-and-interdependence4-1-dna-genes-and-chromosomes7 主题
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4-2-dna-and-protein-synthesis6 主题
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4-3-genetic-diversity-mutations-and-meiosis7 主题
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4-4-genetic-diversity-and-adaptation6 主题
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4-5-species-and-taxonomy4 主题
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4-6-biodiversity9 主题
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5-energy-transfers-in-and-between-organisms-a-level-only5-1-photosynthesis-a-level-only5 主题
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5-2-respiration-a-level-only7 主题
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5-3-energy-and-ecosystems-a-level-only9 主题
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5-4-nutrient-cycles-a-level-only4 主题
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6-organisms-respond-to-changes-in-their-environments-a-level-only6-1-response-to-stimuli-a-level-only12 主题
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6-1-1-survival-and-response
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6-1-2-growth-factors-in-flowering-plants
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6-1-3-indoleacetic-acid-iaa
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6-1-4-taxes-and-kinesis
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6-1-5-reflex-arcs
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6-1-6-required-practical-investigating-animal-movement
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6-1-7-the-pacinian-corpuscle
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6-1-8-pacinian-corpuscles-generator-potential
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6-1-9-investigating-touch-and-temperature-receptors
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6-1-10-the-human-retina
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6-1-11-myogenic-stimulation-of-the-heart
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6-1-13-heart-rate
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6-1-1-survival-and-response
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6-2-nervous-coordination-a-level-only10 主题
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6-3-skeletal-muscles-a-level-only6 主题
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6-4-homeostasis-a-level-only11 主题
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6-4-1-principles-of-homeostasis
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6-4-2-negative-feedback
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6-4-3-glucose-concentration-and-insulin
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6-4-4-glucose-regulation-glucagon
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6-4-5-glucose-regulation-adrenaline
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6-4-6-glucose-regulation-the-liver
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6-4-7-diabetes
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6-4-8-required-practical-determining-the-concentration-of-glucose-in-urine
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6-4-9-nephron-structure
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6-4-10-nephron-function
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6-4-11-control-of-blood-water-potential
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6-4-1-principles-of-homeostasis
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7-genetics-populations-evolution-and-ecosystems-a-level-only7-1-inheritance-a-level-only6 主题
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7-2-populations-a-level-only3 主题
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7-3-evolution-a-level-only5 主题
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7-4-populations-in-ecosystems-a-level-only7 主题
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8-the-control-of-gene-expression-a-level-only8-1-genetic-mutations-a-level-only2 主题
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8-2-regulation-of-gene-expression-a-level-only11 主题
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8-2-1-totipotent-cells
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8-2-2-stem-cells
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8-2-3-the-use-of-stem-cells
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8-2-4-producing-tissue-cultures-of-explants
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8-2-5-regulation-of-transcription
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8-2-6-evaluating-data-about-genetic-expression
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8-2-7-epigenetics
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8-2-8-epigenetics-and-disease
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8-2-9-rna-interference
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8-2-10-two-types-of-tumours
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8-2-11-tumour-development
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8-2-1-totipotent-cells
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8-3-using-genome-projects-a-level-only4 主题
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8-4-gene-technologies-a-level-only13 主题
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8-4-1-recombinant-dna-technology
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8-4-2-producing-fragments-of-dna
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8-4-3-investigating-the-specificity-of-restriction-enzymes
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8-4-4-polymerase-chain-reaction
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8-4-5-culture-of-transformed-host-cells
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8-4-6-uses-of-recombinant-dna-technology
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8-4-7-dna-probes-and-dna-hybridisation
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8-4-8-screening-patients
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8-4-9-genetic-counselling-and-personalised-medicine
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8-4-10-variable-number-tandem-repeats
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8-4-11-gel-electrophoresis
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8-4-12-genetic-fingerprinting
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8-4-13-uses-of-genetic-fingerprinting
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8-4-1-recombinant-dna-technology
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exam-guidance-and-skillsessay-guidance3 主题
7-2-2-gene-pools-and-allele-frequency
Gene pools & allele frequency
Gene pools
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A gene pool is the collection of genes within an interbreeding population at a particular time
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As these genes can have different alleles, a gene pool can also be thought of as:
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The sum of all the alleles of the genes of a population (of a single species) at a particular time
Allele frequency
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How often different alleles occur in the gene pool of a population is known as the allele frequency
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Allele frequencies can change over time due to processes such as natural selection
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When the gene pool (or allele frequencies) within a species population changes sufficiently over time, the characteristics of the species population will also change
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Over time, these changes lead to evolution or can become so great that a new species forms
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Collecting data about the frequency of a phenotype
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Phenotype frequency is the number of individuals in a population showing a particular observable trait
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Many organisms have traits that show more than one phenotype (e.g. shell colour in banded snails can be pink or yellow and flower colour in pea plants can be purple or white)
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We calculate the phenotype frequency by:
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Counting individuals showing a specific phenotype
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Dividing by the total number of individuals in the population (or sample)
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The answer is usually expressed as a percentage
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Phenotype frequency = (total individuals with phenotype ÷ total individuals in population) × 100
Worked Example
In a population of 9 pea plants, 7 of the plants have purple flowers, whilst 2 have white flowers.
Calculate the phenotype frequencies of purple and white flowers. Give your answers as percentages.
Step 1: Calculate the phenotype frequency of purple flowers
Phenotype frequency = (total individuals with phenotype ÷ total individuals in population) × 100
= (7 ÷ 9) × 100
= 0.78 × 100
= 78%
Step 2: Calculate the phenotype frequency of white flowers
Phenotype frequency = (total individuals with phenotype ÷ total individuals in population) × 100
= (2 ÷ 9) × 100
= 0.22 × 100
= 22%