Strawberries, like all living organisms, possess DNA. This fundamental molecule contains the instructions for an organism’s development, function, and reproduction.
What is DNA?
DNA, or deoxyribonucleic acid, is the hereditary material found in humans and almost all other organisms. It functions as an instruction manual, providing the code that guides an organism’s growth, how it functions, and how it reproduces. The information within DNA is stored as a specific code formed by four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T).
These bases pair up in a precise way—A with T, and C with G—and are attached to a sugar molecule and a phosphate molecule. These units, called nucleotides, are arranged into two long strands that twist around each other, forming a structure known as a double helix. This double helix resembles a twisted ladder, with the base pairs forming the rungs and the sugar-phosphate molecules creating the vertical sidepieces.
Strawberries: A Living Story
As living plants, strawberries inherently contain DNA within their cells. This genetic material is a universal characteristic of all life on Earth, allowing organisms to grow, metabolize, and reproduce.
Strawberries are particularly well-suited for DNA extraction demonstrations because they are octoploid. This means each strawberry cell contains eight copies of each chromosome, unlike human cells which typically have two. Having multiple sets of chromosomes results in a significantly larger amount of DNA per cell, making it easier to observe the extracted genetic material with the naked eye.
Seeing the Invisible: Extracting Strawberry DNA
Extracting DNA from strawberries is a common and accessible experiment that can be performed using simple household materials. The process typically involves mashing the strawberries, adding a solution containing dish soap and salt, and then layering cold alcohol on top.
Mashing the strawberries physically breaks down the plant’s rigid cell walls and separates the cells.
Dish soap, acting as a detergent, dissolves the fatty cell and nuclear membranes within the strawberry cells. These membranes are made of lipids, and the soap breaks them apart, releasing the DNA and other cellular contents into the solution.
Salt neutralizes the negative charges on the DNA molecules, allowing them to clump together more easily. It also helps separate the DNA from bound proteins, ensuring these proteins remain dissolved.
After filtering the mixture to remove solid debris, cold alcohol, such as isopropyl alcohol or ethanol, is carefully added. DNA is soluble in water but not in alcohol, especially cold alcohol. As the alcohol forms a layer above the strawberry mixture, the DNA precipitates out of the solution and becomes visible as a white, stringy, or cloudy substance at the interface between the two layers. This visible mass is the collected strawberry DNA.