Strawberry DNA Extraction Procedure
Introduction
Have you ever wondered how scientists extract DNA from an organism? All living organisms have
DNA, which is short for deoxyribonucleic acid; it is basically the blueprint for everything that happens inside
an organism’s cells. Overall, DNA tells an organism how to develop and function, and is so important that this
complex compound is found in virtually every one of its cells. In this activity you’ll make your own DNA
extraction kit from household chemicals and use it to separate DNA from strawberries. The objective is to be
able to visualize DNA and gain understanding about how it is packaged in the cell.
Background
Whether you’re a human, rat, tomato or bacterium, each of your cells will have DNA inside of it (with
some rare exceptions, such as mature red blood cells in humans). Each cell has an entire copy of the same set
of instructions, and this set is called the genome. Scientists study DNA for many reasons: They can figure out
how the instructions stored in DNA help your body to function properly. They can use DNA to make new
medicines or genetically modify crops to be resistant to insects. They can solve who is a suspect of a crime,
and can even use ancient DNA to reconstruct evolutionary histories!
To get the DNA from a cell, scientists typically rely on one of many DNA extraction kits available
from biotechnology companies. During a DNA extraction, the strawberries will be crushed up, this helps to
break apart the strawberry cells from each other. Cell walls of the strawberry cells are the next barrier and you
will add salt to this step to help break them up. Then a detergent (soap) will be added, this will cause the cell
membranes to pop open, or lyse, so that the DNA and all of the proteins holding it are released into solution.
Then alcohol added to the solution causes the DNA to precipitate out, in other words, separating it from the
proteins and the nuclei and allowing us to see it as a solid.
Each strawberry cell has eight copies of the genome, giving them a lot of DNA per cell. (Most
organisms only have one genome copy per cell.) In fact, one of the reasons we use strawberries to help
demonstrate DNA extraction is because of the enormous amount of DNA they possess. The other reason
strawberries are used is because ripe strawberries produce an enzyme (fancy protein) that helps to break down
their own cell walls, this makes it easier for us to extract the DNA inside.
Follow the procedure given and then take some time to answer the follow up questions. These
questions demonstrate what you learned and got from the lab so be sure to take your time and answer them as
completely as possible.
Follow up Questions
1. Why were strawberries used in this lab and not another organism?
2. Why did we bother to do this lab activity? What was the objective?
3. This lab had four primary steps, what were they?
4. What was the purpose of each step listed in number 3?
5. Draw a picture showing where DNA is found in a strawberry cell.