100 Days of science #89, 90, & 91- DNA Experiments

We studied quite a bit about DNA this year and I could not believe it when I realized that we had totally forgotten to do these fun DNA experiments I had picked out! I decided there was not time like the present and gathered all the materials we needed.

Before starting any of the experiments I did ask the boys to tell me everything they could remember about DNA and I was pleasantly surprised at all that they had retained from our readings. We quickly moved onto the experiments.

First we did a strawberry DNA extraction.

Using a strawberry, some rubbing alcohol, water, and dish soap we were able to extract (a few!) DNA strands from the strawberry.

We put our rubbing alcohol in the freezer for about 20 minutes; it needs to be cold to work properly.

Meanwhile in a small glass we combined 6 Tablespoons of tap water with 2 tsp. of dish soap and just a pinch of salt.

With our solution all ready to go we set it aside and began working on smooshing up our strawberry. We put it in a Ziploc bag and used our fingers to break it into fine pieces; making sure to keep most of the strawberry at the bottom of the bag.

We added our soap/water solution to the bag and mixed it around a bit.

Using an empty glass we rubber-banded a piece of paper towel over the opening and made a well in the center to catch all our strawberry mess. Any sort of mesh strainer would work too. You just want to collect some of the strawberry juices in the bottom of the glass.

To that juice you'll add a bit of the cold alcohol. Since we were using a small glass I poured enough alcohol to reach mid-way up the glass but you're really just looking for long strands to separate from the juices and float up into the alcohol--- those strands are your DNA!

We use a toothpick to scoop some up... they look a bit like pink boogers (not gonna lie that is what all three of my boys compared them to and they're right!).

We scooped up a second batch of DNA and added it to a test tube of alcohol we had prepared; just to watch it float around and see what it would do.

Second, we took a strand of DNA and put it on a microscope slide. We tried looked at our strand of DNA under the microscope. Now we knew we would never see the double helix that all the books show since you need a very, very powerful microscope to do that but we still wanted to see what it would look like anyway!

We hypothesized that the circles are where the soap bubbles were and all the lines around it are most likely DNA strands.

Finally, we used gumdrops, toothpicks, and twizzles to make our own model DNA strand.

First we separated our gumdrops by color and I had each boy pick 4 colors they were going to use on the whole strand.

Then I had them assign each color to one of the DNA bases: Thymine, Adenine, Guanine, and Cytosine. (which they all labeled as T, A, G, C).

We talked about how the T&A always pair together and the G&C always pair together but that using just these two pairings there are infinite numbers of ways that DNA strands are combined... Then I let them go to work and make their own.