The observations of Brassica rapa in class revealed a variation in color. Brassica rapa, also called fast plants, was studied because as their name suggests, they are able to complete a lifecycle in a short period of time. (www.fastplants.org) The color variations we observed among the plants were that some had green stalks while others were purple. The pigment which gives plants their color is called anthocyanin. (www.carnivorousplants.org) Anthocyanin is responsible for the variety of colors seen in plants. The anthocyanin pigment serves two purposes for plants. Plants use the color to attract insects to facilitate reproduction. The pigment also serves as a sun block, protecting the plants DNA from UV damage from the sun. What was the inheritance system for the differing pigmentations? Was green the dominant allele or was purple the dominant allele? Or does Brassica rapa exhibit incomplete dominance which would result in a brown colored pigment? An experiment was needed in order to determine how the pigment was inherited.
It was expected that if the allele which provided the green pigment was dominant than all the F1 generation would be green. Alternatively, if the allele which is responsible for purple is dominant, than all the F1 plants should be purple. If the plant exhibited incomplete dominance than the F1 generation should all be brown, a hybrid of purple and green. (Biology) Once an F1 generation was produced, we could then crossbreed to see what phenotypic ratios the F2 Brassica rapa exhibited. If green pigmentation was dominant, we could expect to see a 3:1 ratio of green to purple plants. If purple pigmentation was dominant, we would see a 3:1 ratio of purple to green. If there was incomplete dominance between green and purple alleles, a ration of 1:2:1 of green:brown:purple would be expected.
The experiment consisted of eight seeds of true breeding green and... [continues]
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