27. (4 PTS) You are studying pollination in the plant Arabidopsis, and you have found a mutation in a gene for stamen length that produces a very long stamen in these flowers. You are interested in crossing these to a mutation from a different lab that produces shorter petals, to see how this combination would affect pollinators like honey bees. When you look these genes up you find they are 24cM apart on Chromosome 12. You contact the other lab and they send you their true-breeding plants with short petals and normal stamens. You cross these to your long stamen plants, and all of the F1’s have short petals and normal stamens. You then cross the F1’s to your long stamen plants. If you collect 100 plants from this cross how many do you expect to have short petals and long stamens?

12

Explanation:

Parent 1 : normal petal, long stamen

Parent 2 : short petal, normal stamen

F1 generation has all short petal and normal stamen plants so these two are the dominant traits.

F2 generation will have a mixed progeny. Out of them normal petal, long stamen and short petal, normal stamen will be parental combinations since they were the phenotype of the original parents.

Distance between the two genes is 24 cM and distance between genes = recombination frequency. Hence, recombination frequency here is 0.24.

Out of 100 total plants in F2, 100*0.24 = 24 will be recombinants. Out of 24, 12 will be short petal, long stamen recombinants and other 12 will be normal petal, normal stamen recombinants.

Hence, out of 100 plants 12 are expected to have short petals and long stamens.

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