Friday, January 16, 2015

Punnett Square Cookies

Punnett Squares are fun. Cookies are even more fun. We got the idea to combine the two from this blog post.

Here are two videos that explain how to use Punnett Squares. Because we are very attached to bears after our bear unit, we also liked this Punnett Square showing how the white bears called "spirit bears" come by their white coloration.

For this activity, I just made our favorite chocolate chip cookie dough recipe, and left out the chocolate chips. Then, for the chocolate dough, I made another batch of the same dough and added 1/2 cup of cocoa to it instead of 1/2 cup of the flour. Sugar cookie dough, obviously, would work fine too, but we quite liked the flavor of these.
One of the things I liked about this activity was how well it demonstrated the idea of the dominant allele "masking" the recessive allele. If you take a ball of light dough and a ball of dark dough (representing the two forms of the gene), and mix them together (just squish them around until they are combined), you can see that the resulting phenotype is dark, just like the original dominant allele.
After trying that, though, we didn't actually mix the two alleles together. We just left both alleles showing in our Punnett squares, so we could see the genotypes and not just the phenotypes.
And when we had finished filling out the Punnett squares, we mixed the dough together somewhat randomly to make the cookies. It resulted in some nice marbling. :) Fun!

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