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Biology AS CIE
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1-cell-structure10 主题
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1-2-cells-as-the-basic-units-of-living-organisms AS viruses
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1-2-cells-as-the-basic-units-of-living-organisms AS prokaryotic-v-eukaryotic-cells
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1-2-cells-as-the-basic-units-of-living-organisms AS the-vital-role-of-atp
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1-2-cells-as-the-basic-units-of-living-organisms AS animal-and-plant-cells
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1-2-cells-as-the-basic-units-of-living-organisms AS eukaryotic-cell-structures-and-functions
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1-1-the-microscope-in-cell-studies AS calculating-actual-size
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1-1-the-microscope-in-cell-studies AS resolution-and-magnification
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1-1-the-microscope-in-cell-studies AS eyepiece-graticules-and-stage-micrometers
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1-1-the-microscope-in-cell-studies AS magnification-calculations
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1-1-the-microscope-in-cell-studies AS the-microscope-in-cell-studies
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1-2-cells-as-the-basic-units-of-living-organisms AS viruses
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2-biological-molecules19 主题
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2-4-water AS water-and-the-hydrogen-bond
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2-4-water AS the-role-of-water-in-living-organisms
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2-3-proteins AS collagen
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2-3-proteins AS haemoglobin
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2-3-proteins AS globular-and-fibrous-proteins
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2-3-proteins AS protein-shape
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2-3-proteins AS the-four-levels-of-protein-structure
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2-3-proteins AS amino-acids-and-the-peptide-bond
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2-2-carbohydrates-and-lipids AS phospholipids
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2-2-carbohydrates-and-lipids AS triglycerides
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2-2-carbohydrates-and-lipids AS cellulose
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2-2-carbohydrates-and-lipids AS starch-and-glycogen
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2-2-carbohydrates-and-lipids AS the-glycosidic-bond
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2-2-carbohydrates-and-lipids AS reducing-and-non-reducing-sugars
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2-2-carbohydrates-and-lipids AS covalent-bonds-in-polymers
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2-2-carbohydrates-and-lipids AS biological-molecules-key-terms
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2-1-testing-for-biological-molecules AS testing-for-non-reducing-sugars
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2-1-testing-for-biological-molecules AS the-benedicts-test
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2-1-testing-for-biological-molecules AS biological-molecule-tests
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2-4-water AS water-and-the-hydrogen-bond
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3-enzymes13 主题
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3-2-factors-that-affect-enzyme-action AS enzyme-activity-immobilised-v-free
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3-2-factors-that-affect-enzyme-action AS enzyme-inhibitors
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3-2-factors-that-affect-enzyme-action AS vmax-and-the-michaelis-menten-constant
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3-2-factors-that-affect-enzyme-action AS rate-inhibitor-concentration
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3-2-factors-that-affect-enzyme-action AS rate-substrate-concentration
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3-2-factors-that-affect-enzyme-action AS rate-enzyme-concentration
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3-2-factors-that-affect-enzyme-action AS rate-ph
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3-2-factors-that-affect-enzyme-action AS rate-temperature
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3-1-mode-of-action-of-enzymes AS colorimetry
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3-1-mode-of-action-of-enzymes AS measuring-enzyme-activity
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3-1-mode-of-action-of-enzymes AS how-enzymes-work
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3-1-mode-of-action-of-enzymes AS enzyme-action
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3-1-mode-of-action-of-enzymes AS enzymes
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3-2-factors-that-affect-enzyme-action AS enzyme-activity-immobilised-v-free
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4-cell-membranes-and-transport16 主题
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4-2-movement-into-and-out-of-cells AS comparing-osmosis-in-plants-and-animals
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4-2-movement-into-and-out-of-cells AS osmosis-in-animals
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4-2-movement-into-and-out-of-cells AS osmosis-in-plant-cells
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4-2-movement-into-and-out-of-cells AS estimating-water-potential-in-plants
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4-2-movement-into-and-out-of-cells AS investigating-surface-area
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4-2-movement-into-and-out-of-cells AS surface-area-to-volume-ratios
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4-2-movement-into-and-out-of-cells AS investigating-diffusion
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4-2-movement-into-and-out-of-cells AS investigating-transport-processes-in-plants
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4-2-movement-into-and-out-of-cells AS endocytosis-and-exocytosis
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4-2-movement-into-and-out-of-cells AS active-transport
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4-2-movement-into-and-out-of-cells AS osmosis
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4-2-movement-into-and-out-of-cells AS diffusion
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4-1-fluid-mosaic-membranes AS cell-signalling
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4-1-fluid-mosaic-membranes AS the-cell-surface-membrane
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4-1-fluid-mosaic-membranes AS components-of-cell-surface-membranes
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4-1-fluid-mosaic-membranes AS the-fluid-mosaic-model
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4-2-movement-into-and-out-of-cells AS comparing-osmosis-in-plants-and-animals
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5-the-mitotic-cell-cycle8 主题
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5-2-chromosome-behaviour-in-mitosis AS observing-mitosis
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5-2-chromosome-behaviour-in-mitosis AS the-stages-of-mitosis
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5-1-replication-and-division-of-nuclei-and-cells AS how-tumours-form
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5-1-replication-and-division-of-nuclei-and-cells AS the-role-of-stem-cells
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5-1-replication-and-division-of-nuclei-and-cells AS the-role-of-telomeres-
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5-1-replication-and-division-of-nuclei-and-cells AS the-cell-cycle
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5-1-replication-and-division-of-nuclei-and-cells AS mitosis
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5-1-replication-and-division-of-nuclei-and-cells AS chromosome-structure
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5-2-chromosome-behaviour-in-mitosis AS observing-mitosis
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6-nucleic-acids-and-protein-synthesis9 主题
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6-2-protein-synthesis AS gene-mutations
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6-2-protein-synthesis AS transcription
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6-2-protein-synthesis AS constructing-polypeptides
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6-2-protein-synthesis AS the-universal-genetic-code
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6-2-protein-synthesis AS from-gene-to-polypeptide
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6-1-structure-of-nucleic-acids-and-replication-of-dna AS the-structure-of-rna
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6-1-structure-of-nucleic-acids-and-replication-of-dna AS semi-conservative-dna-replication
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6-1-structure-of-nucleic-acids-and-replication-of-dna AS the-structure-of-dna
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6-1-structure-of-nucleic-acids-and-replication-of-dna AS nucleotides
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6-2-protein-synthesis AS gene-mutations
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7-transport-in-plants11 主题
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7-2-transport-mechanisms AS phloem-mass-flow
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7-2-transport-mechanisms AS the-sucrose-loading-mechanism
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7-2-transport-mechanisms AS movement-in-the-phloem
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7-2-transport-mechanisms AS xerophytic-plant-leaf-adaptations
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7-2-transport-mechanisms AS water-and-the-transpiration-pull
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7-2-transport-mechanisms AS transpiration-in-plants
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7-2-transport-mechanisms AS water-and-mineral-ion-transport-in-plants
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7-1-structure-of-transport-tissues AS phloem-sieve-tube-elements
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7-1-structure-of-transport-tissues AS xylem-vessels-elements
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7-1-structure-of-transport-tissues AS xylem-and-phloem-distribution
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7-1-structure-of-transport-tissues AS plant-transverse-sections
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7-2-transport-mechanisms AS phloem-mass-flow
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8-transport-in-mammals16 主题
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8-3-the-heart AS heart-action
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8-3-the-heart AS the-cardiac-cycle
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8-3-the-heart AS the-walls-of-the-heart
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8-3-the-heart AS structure-of-the-heart
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8-2-transport-of-oxygen-and-carbon-dioxide AS the-bohr-shift
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8-2-transport-of-oxygen-and-carbon-dioxide AS the-oxygen-dissociation-curve
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8-2-transport-of-oxygen-and-carbon-dioxide AS plasma-and-carbon-dioxide
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8-2-transport-of-oxygen-and-carbon-dioxide AS the-chloride-shift
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8-2-transport-of-oxygen-and-carbon-dioxide AS red-blood-cells-haemoglobin-and-oxygen
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8-1-the-circulatory-system AS blood-tissue-fluid-and-lymph
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8-1-the-circulatory-system AS the-role-of-water-in-circulation
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8-1-the-circulatory-system AS cells-of-the-blood
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8-1-the-circulatory-system AS blood-vessels-structures-and-functions
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8-1-the-circulatory-system AS observing-and-drawing-blood-vessels
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8-1-the-circulatory-system AS the-main-blood-vessels
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8-1-the-circulatory-system AS circulatory-systems
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8-3-the-heart AS heart-action
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9-gas-exchange6 主题
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9-1-the-gas-exchange-system AS gas-exchange-processes
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9-1-the-gas-exchange-system AS structures-and-functions-of-the-gas-exchange-system
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9-1-the-gas-exchange-system AS recognising-structures
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9-1-the-gas-exchange-system AS recognising-tissues
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9-1-the-gas-exchange-system AS distribution-of-tissues
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9-1-the-gas-exchange-system AS the-human-gas-exchange-system
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9-1-the-gas-exchange-system AS gas-exchange-processes
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10-infectious-diseases6 主题
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11-immunity10 主题
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11-2-antibodies-and-vaccination AS vaccination-to-control-disease
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11-2-antibodies-and-vaccination AS how-vaccines-work
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11-2-antibodies-and-vaccination AS types-of-immunity
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11-2-antibodies-and-vaccination AS uses-of-monoclonal-antibodies
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11-2-antibodies-and-vaccination AS making-monoclonal-antibodies
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11-2-antibodies-and-vaccination AS antibodies
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11-1-the-immune-system AS memory-cells-and-immunity
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11-1-the-immune-system AS primary-immune-response
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11-1-the-immune-system AS antigens
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11-1-the-immune-system AS phagocytes
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11-2-antibodies-and-vaccination AS vaccination-to-control-disease
课 5,
主题 5
In Progress
5-1-replication-and-division-of-nuclei-and-cells AS the-role-of-telomeres-
课 Progress
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Exam code:9700
The significance of telomeres
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The ends of the chromatids in chromosomes are ‘sealed’ with protective structures called telomeres
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They are made of non-coding DNA (DNA that does not contain genes) that is made up of short base sequences that are repeated many times (multiple repeat sequences)
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The main function of telomeres is to ensure that the very ends of the DNA molecules are included in DNA replication during mitosis
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This is because the copying enzyme responsible for DNA replication is unable to run right to the very end of the DNA molecule and stops a little short of the end
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If this end part of the DNA molecule contained an important gene, that piece of genetic information would be lost during DNA replication
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In each subsequent cell division, a little more genetic information would be lost
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Telomeres therefore act as a ‘buffer’ region of non-essential DNA
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They ensure that no important coding sections near the ends of the DNA molecules are left out of the replication process
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This ensures no genes are lost during cell division (the loss of vital genes can even result in cell death) and allows for continued replication of a cell
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Examiner Tips and Tricks
Telomeres are similar to the coding regions of DNA molecules in that they are made of the same nucleotides. However, telomeres’ base sequences are non-coding, meaning they do not code for proteins.
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