Continuing with our secret code theme in the Whodunnit class, I presented DNA as the secret code of life. I explained the basics of DNA molecular structure and emphasized the "code" that was created by the 4 different nucleotides. The cipher for our secret code is C=G and A=T (cytosine always pairs with guanine and adenine with thymine in the double helix).
We created this DNA Model using chenille stems (pipe cleaners) and pony beads. The original directions for this activity (see link above) used fishing line or plastic thread in order to make a bracelet, which I thought might not be too interesting for the boys in the class or easy for students with fine motor skill issues. I had the students bend one end of the pipe cleaner so the beads would not fall off while they were working. The Ology site provided a short list of animal and plant gene sequences (the pipe cleaners can hold 40 beads well) which I typed up for the students. The first step was to decode the other strand of DNA using the cipher C=G and A=T. Then the students could chose 4 different color beads assigning one color to each of the 4 nucleotide bases (i.e. in the model shown blue=thymine, orange=adenine, green=cytosine and pink=guanine). The visual aid helped to cement the concept of base pairing, every time I use a pink(guanine) on the other strand of DNA there will be a green (cytosine) to pair up with it when the two strands are placed next to one another. The last step was to twist the two strands together to create the helix.
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