What is DNA? DNA stands for deoxyribonucleic acid. DNA is a molecule in the form of a double helix - two spirals twisting around each other. These spirals are the backbone of the DNA, and are made up of sugars and phosphates. The spirals are connected by chemicals known as bases, which stretch between the spirals like the rungs of a ladder. DNA has four types of bases: adenine (A), thymine (T), guanine (G) and cytosine (C). A and T always join together, as do G and C. What does DNA do? DNA is the genetic “instruction manual” for making an organism. All processes in the organism are controlled by DNA. A gene is a sequence of DNA. A gene represents the instruction a cell uses to make a specific protein. Why do we use detergent? The detergent bursts open the cells of the fruit, releasing the DNA. The soap helps to dissolve the phospholipid bilayers of the cell membrane and organelles. You can observe how detergent “cuts” through lipids (fats and waxes) when you wash greasy dishes in your sink! Why do we use the salt? The salt is used to keep the concentration of salt similar inside and outside of the cell. This keeps the DNA intact and helps it to clump together once the cell is broken open. Why do we use the ethanol? When molecules are insoluble (unable to be dissolved), they clump together and can become visible. DNA is not soluble in ethanol. Therefore, ethanol causes the DNA strands to clump together (precipitate) and become visible to the naked eye. The colder the ethanol, the less soluble the DNA will be in it. Thus, if you cool the ethanol it will help precipitate the DNA!

EXTRACT PLANT DNA All living things have DNA, the chemical instructions for how to make a living thing. When collected from thousands of cells, DNA can be seen with the naked eye!

Australian Curriculum Links: Year 8: ACSSU149; Year 10: ACSSU184; Senior secondary curriculum: Biology Unit 2, Unit 4.

PEB on social media: Document prepared by the ARC Centre of Excellence in Plant Energy Biology