Key term
Edexcel GCSE Combined Science Biology 1SC0
Key Concepts in Biology
Topic overviewEukaryotic and prokaryotic cellsSpecialised cells and their adaptationsMicroscopes and magnification calculationsSize, scale and units in cell biologyEnzyme action and denaturationFactors affecting enzyme activityEnzymes in synthesis and digestion, and rate calculationsDiffusion, osmosis and active transportOsmosis in potatoes and percentage change in mass
Cells and Control
Genetics
Topic overviewMeiosis and the formation of gametesDNA structure, genes and the genomeExtracting DNA from fruitAlleles, genotype and phenotypeMonohybrid crosses and sex determinationProbability and ratios from genetic crossesCauses of variation: genes and environmentThe Human Genome ProjectGenetic variation and the effects of mutation
Natural Selection and Genetic Modification
Health, Disease and the Development of Medicines
Topic overviewHealth, disease and susceptibilityPathogens and common infectionsHow pathogens spread, and the virus life cycleSexually transmitted infectionsPhysical barriers and chemical defencesThe immune system, immunisation and herd immunityAntibiotics and developing new medicinesLifestyle factors and non-communicable diseaseTreatments for cardiovascular disease
Plant Structures and Their Functions
Animal Coordination, Control and Homeostasis
Exchange and Transport in Animals
Topic overviewWhy multicellular organisms need exchange surfacesAlveoli and gas exchangeThe blood and its componentsArteries, veins and capillariesThe heart and the circulatory systemCellular respiration as an exothermic reactionAerobic and anaerobic respiration comparedInvestigating the rate of respirationCardiac output, stroke volume and heart rate
Ecosystems and Material Cycles
Genetics
Extracting DNA from fruit
- 3 things to know
- Paper 1
Overview
Extracting DNA from fruit by mashing, adding detergent and salt, filtering and pouring on ice-cold ethanol, why the DNA comes out of solution as a white stringy layer, and why the mixture is stirred gently.
What you need to know
Answer each one before you reveal it.
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Key term
Why is detergent added to the mashed fruit when extracting DNA?
Key term
Why is salt added to the mixture when extracting DNA from fruit?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Why is fruit such as kiwi mashed at the start of extracting DNA from it?
Model answer
Mashing breaks open the cell walls so the contents of the cells are released.
- 2
Why is detergent added to the mashed fruit when extracting DNA?
Model answer
The detergent breaks down the cell membranes, releasing the DNA into the mixture.
- 3
Why is salt added to the mixture when extracting DNA from fruit?
Model answer
The salt makes the DNA molecules stick together so they can be seen.
- 4
Why is the fruit mixture filtered before the next stage of the extraction?
Model answer
Filtering removes the insoluble pieces of cell debris and leaves the DNA in the liquid.
- 5
Which liquid is poured gently onto the filtered fruit mixture to make the DNA appear?
Model answer
Ice-cold ethanol is poured gently on top.
- 6
Explain why the DNA appears when ice-cold ethanol is added.
Model answer
DNA does not dissolve in cold ethanol, so it comes out of solution as a solid.
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