The key to these problems is to break them down into pieces that are easy to solve and then put the partial solutions together to get the full solution.

Example: Male bumblebee X female pastel

1. Determine the relevant gene pairs.

Male has a pastel mutant gene paired with a normal gene (pastel//normal). The equivalent gene pair in the female has a pastel mutant gene paired with a normal gene (pastel//normal).

Male has a spider mutant gene paired with a normal gene (spider//normal). The equivalent gene pair in the female has two normal genes (normal//normal).

2. Use a Punnett square, FOIL, or other technique to determine the result of the mating for the first gene pair. Repeat to determine the result of the mating for the second gene pair. Repeat for each additional gene pair.

pastel//normal X pastel//normal -->
1/4 pastel//pastel (= super pastel)
2/4 pastel//normal (= pastel)
1/4 normal//normal (= normal)

spider//normal X normal//normal -->
1/2 spider//normal (= spider)
1/2 normal//normal (= normal)

3. Combine the individual results to get the full result

For the pastel gene pair, all of the babies are either super pastel, pastel, or normal. For the spider gene pair, all of the babies are either spider or normal. So all of the super pastel babies are either spider or normal, all the pastel babies are either spider or normal, and all the normal babies are either spider or normal. The combination fractions are found by multiplying the individual fractions.

1/4 super pastel -- 1/2 spider = 1/8 super pastel spider (killer bee)
1/4 super pastel -- 1/2 normal = 1/8 super pastel
2/4 pastel -- 1/2 spider = 2/8 pastel spider (bumblebee)
2/4 pastel -- 1/2 normal = 2/8 pastel
1/4 normal -- 1/2 spider = 1/8 spider
1/4 normal -- 1/2 normal = 1/8 normal

Clear as mud?

Paul Hollander

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