Year 9 have been extracting DNA from strawberry cells in class today.
DNA is present in every cell of all plants and animals and determines all genetic traits of the individual organism. The long thick fibres that we pulled out of the extraction mixture are real strands of strawberry
Strawberries are the perfect choice for a DNA extraction experiments for two very good reasons:
(1) they yield way more DNA than other fruits,
(2) they are octoploid, meaning that they have eight copies of each type of DNA chromosome. (Human cells are generally diploid, meaning two sets of chromosomes.) These special circumstances make strawberry DNA both easy to extract and to see.
To extract the DNA, each component of the extraction mixture plays a part.
Soap helps to dissolve cell membranes.
Salt is added to release the DNA strands by breaking up protein chains that hold nucleic acids together.
Finally, DNA is not soluble in isopropyl alcohol, especially when the alcohol is ice cold and makes the fibres easy to see.
Click on an image to see some of our reactions.