Self Assessment Question # 3 for Lesson 15

by Dr Jamie Love © 2002 - 2005
Genetics Course

Harebells are a pretty plant that normally produces blue flowers.
(Notice that we have switched to a different species so the genetics will be different. However, as you will see, it is useful to keep in mind what you have just done in SAQ 1 and 2.)

A fellow in Britain sends you some white-flowered harebells and explains they are from a true-breeding population that he has been growing in his garden for many years. (The offspring from mating these have always produced white-flowered harebells, just like the parents.) Let's call these the "British (white-flowered) harebells".
A woman in the USA has also developed a true-breeding population of white-flowered harebells and sends them to you. They have the exact phenotypes and breeding qualities as the British plants. We will call these the "American (white-flowered) harebells".
You mate these two populations, moving the pollen from a British white-flowered harebell onto the stigma of an American white-flowered harebell. And you do the reciprocal cross too, because you are a good geneticist and want to know if there is anything funny going on. Regardless, crosses in either direction give you all blue-flowered offspring!

Explain this surprising result.
Use the ideas in SAQ 1 and 2 to help you. Start by drawing a possible pathway that might explain these results. (Hint, it is NOT a requirement that magenta be an intermediate to blue.) This is not a particularly easy question but give it some thought.
Once you have done that, assign genotypes to the two original true-breeding populations and to the blue-flowered hybrid you just created.

Go to the ANSWER

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