All living things come with a set of instructions stored in their deoxyribonucleic acid (DNA), that determine the way you look and how your body functions. Whether you are a human, cat, strawberry, or bacteria, each cell has DNA contained in it (with some extremely rare exceptions), and is located in the cell nucleus. DNA contains the instructions needed for an organism to develop, survive and reproduce. It is the blueprint for everything that happens inside the cell of an organism, each cell has an entire replica of the same set of DNA. The entire set of DNA in an organism is called the genome. The DNA found in strawberry and kiwi fruit cells can be extracted using common, everyday materials such as detergent, salt and rubbing alcohol.
DNA is a large molecule that is made up of smaller components called nucleotides. Each nucleotide has three parts: a phosphate molecule, a sugar molecule and one of four nitrogenous bases. The base of the nucleotide is the part that carries the genetic information. The four bases found in DNA are adenine, cytosine, guanine, and thymine. The nucleotides are organized in a way that makes DNA a double helix. The nitrogen bases being the ‘rungs’ on the double helix, and the upright of the ‘ladder’ are made up of alternating phosphate and sugar groups.
Scientists extract and study DNA for many reasons including to figure out how instructions stored in DNA help your body to function properly, to make new medicines, to genetically modify foods to be resistant to insects, to figure out the suspect of a crime. To find cures for diseases by experimenting with DNA, correctly sort organisms into classes because of DNA differences. Also scientist can genetically engineer certain organisms to produce beneficial things that can help living organisms to function correctly e.g. Scientists can genetically engineer insulin production so that people with diabetes can live for longer.
Aim: To extract, isolate and observe DNA in kiwi fruit and strawberries.
Hypothesis: During this experiment when the DNA extracting solution is added to the fruits, the DNA found in the kiwi fruit and strawberry will separate from the rest of the fruit.
Rubbing alcohol in your eyes
Wear safety glasses whilst executing experiment
Glass (test tube, beaker)
Don’t play around glass and be cautious at all times
Hold sharp point downwards and don’t swing around in the air.
Zip-closure sandwich bags
DNA extracting solution (mix about 1 cup of dish detergent and ¼ cup salt into 4½ litres of water)
Denatured alcohol (rubbing alcohol)
1. Place ¼ large kiwi fruit in a zip-lock bag and remove most of the air before you seal the bag.
2. Mash the kiwi fruit through the bag in your hand. Do not hit against the table.
3. Add 20ml of the DNA extracting solution.
4. Continue mixing and mashing the bag in your hand.
5. Place a piece of gauze over the opening of the cup, securing it with a rubber band.
6. Carefully pour out the kiwi fruit mixture into the cup making sure to catch the solids with the gauze.
7. Take the dropper full of the liquid in the cup and place in the test tube.
8. Add a dropper full of the alcohol to the test tube. Take care not to tip or tilt the test tube. Do not mix the two liquids.
9. Observe the line between the kiwi fruit mixture and the alcohol
When the rubbing alcohol was added to the kiwi fruit and strawberry solutions, the different substances remained in separate layers (density). Then the DNA started to rise up from the fruit solutions up into the alcohol and formed a cloudy clump in the middle of the rubbing alcohol layer. After letting the substances sit for a while a new thinner layer of DNA was formed on the very top of the combined substances. This layer of DNA was then able to…