Organic Chemistry Lesson 14 DNA
Extracting DNA from a kiwifruit
DNA (deoxyribonucleic acid) is another important natural polymer that is essential for life. It enables living things to develop and function. DNA’s structure contains a genetic code that determines the different amino acid sequences of every protein in your body. The genetic code can be copied to make protein molecules with exactly the same sequence of amino acids.
Safety
· eye protection
· ethanol: HARMFUL/HIGHLY FLAMMABL
Equipment
· kiwi fruit· sodium chloride
· sieve
· washing-up liquid
· 2 ´ 250 cm3 jar
· fork
· knife
· chopping board
· Ice / · large beaker or basin (for a water bath)
· thermometer
· test tube
· 100 cm3 ice cold ethanol
· glass rod
· paper towel
· 100 cm3 measuring cylinder
· table spoon
· kettle/boiling water
· pineapple juice
Setting the scene
DNA (deoxyribonucleic acid) is an important natural polymer that is essential for life. It enables living things to develop and function. DNA’s structure contains a genetic code that determines the different amino acid sequences of every protein in your body. The genetic code can be copied to make protein molecules with exactly the same sequence of amino acids.
Method.
1 Peel the kiwi fruit, discard the skin, and chop the fruit into small chunks.
2 Put the chunks of fruit in a jar and mash the kiwi as much as you can.
3 Mix together 2 teaspoons of washing-up liquid, half a teaspoon of salt and 80cm3 of water in a beaker and stir slowly until the salt has dissolved. This mixture is known as an extraction buffer.
4 Add the extraction buffer to the mashed-up kiwi and continue mashing. The more you mash, the more DNA you will get out at the end.
5 Incubate the kiwi and buffer mixture at 60 oC for 15 minutes. To make your own incubator, take a large basin and half fill it with boiling water from a kettle. To reduce the temperature, add about the same amount again of normal tap water. Using a thermometer will help you reach a more precise temperature. Carefully put the jar with the kiwi into the incubator and leave to stand for 15minutes
6 Remove the jar from the incubator and filter the kiwi mixture through a fine sieve into another jar. You should be left with a green liquid which contains the kiwi fruit DNA.
7 Add about 15 cm3 of pineapple juice to the green liquid, stir and leave for 5minutes
8 Take the ice cold ethanol and pour it slowly down the side of the jar. The alcohol will form a transparent layer on top of the kiwi mixture, as the alcohol is less dense.