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DNA – Deoxyribonucleic acid
- coiled and folded to fit into the nucleus
- Proteins called histones hold folds
- Double-helix in shape
- Complementary base pairs
- Adenine – Thymine
- Guanine – Cytosine
- At The Giants Causeway
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To Isolate DNA from a plant tissue
- 1.3g sodium chloride to washing up liquid
- 2.Add distilled water so solution is 100cm3
- 3.Cut onion into small cubes
- 4.Add onion to solution
- Detergent - cell membranes break & release DNA
- Salt - causes DNA to clump together
- 5.Put in water bath at 60ºC for 15 mins
- Denatures enzymes
- 6.Cool in ice bath for 5 mins
- Stops DNA breakdown
- 7.Blend mix for 3 seconds
- Breaks down cell walls & releases DNA
- 8.Filter through coffee filter paper
- Filtrate contains DNA & proteins
- 9.Syringe 6cm3 filtrate into boiling test tube
- 10. Add 4 drops protease enzyme
- Breaks down protein around DNA
- 11.Pour 9cm3 ice cold 95% ethanol slowly down side of test tube
- Precipitates DNA out of water
- 12.Twist a small glass rod in test tube
- DNA attaches to rod & form a clear mesh
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Detailed Structure of DNA
3 structures: nucleotides, base pairs & double helix
- 1. Nucleotides
- phosphate group, a sugar & a nitrogen-containing base
- Join together with a bond between phosphate & sugar
- Phosphate Group – PO4
- Sugar - Deoxyribose
- Nitrogenous base – One of Adenine, Guanine (Purine bases), Thymine & cytosine (pyramidine bases)
- 2. Base Pairs
- Adenine & thymine form 2 weak hydrogen bonds
- Guanine & cytosine form 3 weak hydrogen bonds
- Hydrogen bonds: weak bonds formed when slightly positive hydrogen is attracted by another slightly negative atom.
- 3. Double Helix
- Spiral chains of nuceotides
- Outside strands – deoxyribose & phosphate
- Rungs – Base pairs
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