Extracting DNA

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My husband did an experiment with my kids the other night. We had fun extracting DNA from an onion. My 8-year-old son Nathaniel received a DNA kit as a gift, so he was eager to try one of the experiments. First we cut an onion into small pieces, and the kids mashed it in a glass measuring cup. We added half a cup of warm water. Then we added 5 ml of powdered detergent. We stirred it.

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Next we filled a bowl with hot water. We measured the temperature with a thermometer, adding cold water until it was 50 degrees Celcius. We put the measuring cup with the smashed onion bits into the hot water. Then we set the timer for 12 minutes.

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We added hot water as needed, to keep the mixture at 50 degrees, stirring from time to time. Also, we got a second bowl and filled it with ice cubes and water.

Ding. (The timer went off.) We took the mixture out of the hot water and put it into the cold water. We set the timer for 5 more minutes.extracting-dna-3

Ding. We grabbed a coffee filter and stuffed it into a funnel. Then we poured the onion mixture through the filter and funnel, and into a glass. The gunk trapped in the filter included “cell walls, cell membranes, and cytoplasmic leftovers, but not the DNA from the cell.” The DNA passed through the filter.

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We poured the DNA liquid (called supernatant) from the glass into a test tube, filling the tube halfway. We added a pinch of salt, then dripped chilled (denatured) alcohol down the side of the tube, filling the other half of the test tube. We screwed the cap onto the tube and rocked it back and forth like we were dancing with a maracas. We placed the tube in the freezer and waited at least 10 minutes, tapping our feet impatiently.

Ding. Oh my goodness! The white gloppy stuff is DNA! It feels gooey like mucous, and and it’s stringy, like it has formed chains!

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My husband also helped my kids put together a DNA chain with the plastic snap-together DNA pieces. He looked at me and said that he gives this Science Wiz DNA kit a thumbs up. The colorful instructions were easy to follow, and the experiments were fun.

extracting-dna-6Linked to Science Sunday at Adventures in Mommydom:

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One Response to “Extracting DNA”

  1. Ticia says:

    But you didn’t include a link to the cool kit you used, how am I supposed to get it?

    Great post, I loved it. Thanks for linking to Science Sunday!

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