Extraction: DNA from strawberries

Raneen Sawafta/Reuters
A Palestinian worker collects strawberries at a farm in Tubas, in the in the Israeli-occupied West Bank April 30, 2019.

You may hear about scientists analyzing DNA, but have you ever wondered just how they get their hands on it? In this demonstration,  you’ll learn how to use common house-hold items to isolate DNA. 

Materials: 3 strawberries with the stems removed; 1/3 cup water; 1/2 teaspoon salt; 1 tablespoon dishwashing liquid; cheesecloth  or coffee filter; heavy-duty resealable plastic bag; tall narrow glass; chopstick, toothpick, or coffee stirrer; 1/2 cup isopropyl alcohol.

Procedure: Strawberries  are ideal for this demonstration because their cells have eight copies of each chromosome, instead of the usual one, meaning there’s a lot of DNA inside.

Why We Wrote This

The ability to study DNA revolutionized the field of biology. But to study it, scientists first have to extract DNA molecules from the rest of an organism.

To begin, place the alcohol in the freezer. Then, put the strawberries in the plastic bag, along with the salt, water, and soap, and squeeze as much air as you can out of the bag before resealing. Now smush the bag’s contents.

The soap breaks apart the cells in a process called lysing. Cell membranes are made of lipids, which get broken down by the soap like  grease does on a pan. The salt will help the DNA molecules, which are normally too small to see, clump together.

Once your strawberries are thoroughly smashed, strain the liquid into a narrow glass using a cheesecloth or coffee filter.

With the help of a grown-up, carefully pour the chilled alcohol down one side of the glass. Being less dense than the strawberry liquid, the alcohol will float on top.

Look closely at the boundary between the  alcohol and the soapy strawberry juice. The alcohol will cause the salty DNA to precipitate  out of the solution. You should see tiny white  strands that look a little like egg whites. Using a chopstick, toothpick, or coffee stirrer, you can spool the strands and lift them out of the solution. What you’re looking at are millions of DNA molecules, the building blocks of life.  

This column first appeared in the May 27, 2019 edition of The Christian Science Monitor Weekly magazine as part of the Monitor's occasional Science at Home series.

You've read  of  free articles. Subscribe to continue.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to Extraction: DNA from strawberries
Read this article in
QR Code to Subscription page
Start your subscription today