Extracting Strawberry DNA

I invited two Purdue graduate students to come to my class today and help the kids extract DNA from strawberries. It was a huge success.

CP wore his Code Blue mask and hat. (Code Blue is a medical simulation I do with the kids. They set up medical clinics, take board exams, and become doctors. Then we do some diagnosing - it's fun!)

 JR works to get her filter into the tube prior to straining out the DNA from her berry.

 I absolutely love this picture of BP and SR watching their liquid drip through the filter.

 Look at all that DNA in the middle of the test tube!

CM shows off the necklace that contains the DNA that she extracted.

Knowing that I dislike unicorns, ZS, CP, and JK used their necklaces for unicorn horns!

Extracting DNA from Strawberries

On Tuesday, five students from Purdue came to our classroom and led us through a procedure to extract DNA from strawberries.

 Waiting excitedly while materials are given out and the procedure explained.

 First, we had to crush our strawberry slices without breaking their plastic bags.

 It was harder than it looked - the berries needed to be completely broken up into mush.

 We squished and squished and squished!

 Some of the materials brought for us to use (and we got to keep them!)

 The little capped tubes are for storing the extracted DNA.

 After the strawberry slice was sufficiently liquified....

 ... we poured it through a paper towel filter and into a large test tube.

 Making the paper towel filter was tougher than it appeared, too.

 We wrapped the paper towels around our fingers and then tried to gently insert the towel into the large tube.

 Then, a partner helped us to pour the strawberry juice into the tube.

 If you had a tear in your paper towel, you had to begin again as the filter would not work if it was torn.

 After the juice was filtered, we added a solution - surprisingly, it was simply dishwashing liquid.

 And then we watched....

 ... and watched...

 ... until it was time to add ice cold ethyl alcohol.

 The DNA formed into strands and then a ball of matter in the smaller tubes.

 We then used the plastic pipettes to suck up the matter...

 ... which we squirted into the tiny capped tubes to store.

 The DNA is the cloudy matter at the top of the tube.

Finally, we added yarn to the tubes and wore our strawberry DNA as necklaces!

Enjoying Science

It is a darn shame that with all the emphasis Indiana puts on testing in Reading and Math that it has become more and more difficult to teach Science and Social Studies well. I am fortunate in that my curriculum is supposed to be different from general education classes, and that allows me to get in more of those two subjects than my gen ed colleagues do. Still, I wish I could do more.

Tuesday I invited five Purdue students come to my classroom and help my students extract DNA from strawberries. I will write another blog post about that later, but in the meantime, I wanted to post this picture.

This is my student, KR. She loved the DNA project, and was in heaven when the Purdue folk told my students that they could keep the test tubes and other paraphernalia we had used in our experiment. KR's mom sent me this photo of her daughter, saying that she had set up her own experiments that evening at home.

I'm not sure just what she is doing, but knowing KR, it has been well thought out and executed!

That's Me in the Tube!

"Hey, I can now be in two places at once!" crowed one of my boys today. His logic? He'd isolated his own DNA in a centrifuge tube and was joking that he could put the tube somewhere, go elsewhere, and thus be in two spots at once. After all, that was "him" in the centrifuge tube.

Well, it was his DNA, so there was some logic to his premise.

Dr. Andrew DeWoody, a research scientist at Purdue, spent nearly three hours with my class this morning. His area of research is salamander DNA, and he is the father of two of my former students, plus his third daughter, who has Ring 14 (a very rare chromosomal abnormality) is in our reading buddy class.

Dr. DeWoody had offered to come in any time and work with my class, despite the fact that his daughters are now at Harrison and East Tipp. I invited him to come speak with us about DNA, and he brought two post doctoral scientists and did a project to help us isolate our own DNA.

First, though, we did the experiment with strawberries. Strawberries have four times as much DNA as humans do (a bit of a paradox) and so it is much easier to extract theirs.

Step one was to mash our strawberries to a fine pulp in zip lock bags. 

Then we added a soapy liquid (shampoo or dishwashing liquid works well - really!) This further breaks down the cell walls so the strawberries' DNA can be released.

 Then we poured that mixture into a centrifuge tube and added a solution that was 95% alcohol. That would cause the DNA to precipitate after some gentle rocking of the tube. (I love the look on JM's face.)

And there it is! It's the white strands that are gathering in the middle of the tube.

A single strand of DNA in a strawberry cell is a meter long - really! It's coiled tightly inside the cell, and is incredibly tiny.

Then we got a new set of tubes and liquids and set to work on isolating our own DNA. The kids swished a saltwater solution in their mouths for thirty seconds, spat into cups, and then followed the same steps as we did with the strawberries.

 Since human cells have much less DNA than strawberries, and since our sample size was much, much smaller than a strawberry, we did not get nearly as much DNA. Here, Dr. DeWoody shows the kids how to use a bamboo skewer to gather the DNA that has precipitated in their centrifuge tubes.

He and his assistants had tiny little vials to put the kids' DNA in. These were strung on yarn and made into necklaces. It was kind of funny to see the kiddos walking around the rest of the day, "wearing themselves." (Did they get a kick out of that!)

Even better, they can keep their vials indefinitely in the refrigerator or the freezer (He told me that Carobou, who was in his oldest daughter's class from four years ago, still has hers in the freezer!)

It was a nifty way to spend the morning, and I really appreciate Dr. DeWoody's gift of time. And, as he was leaving, he offered to come back in the future!