Unformatted text preview: C, respectively. Then the diploid states for these species are AA, BB, and CC, respectively. Let’s suppose that the first step in the formation of the rye species was fusion of gametes (remember, they are haploid) from the n=5 and n=7 species. The resulting zygote (and eventually the plant that grows from it) can be denoted as AB. This hybrid is sterile, but if there is a chromosome doubling to get to the AABB state, the hybrid will be fertile, forming AB gametes. Now suppose an AB gamete fuses with a C gamete; the resulting zygote and eventually the plant from the zygote would be ABC, and after a second chromosome doubling would be AABBCC and would be fertile, a useful crop species that could then produce viable seeds. Such a hybrid would have an n of 5+7+9=21, just as we see in the rye species. Note that other sequences of hybrid formation ( eg AC or BC formed as the first step) would also work....
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This note was uploaded on 03/03/2010 for the course BIOL 214 taught by Professor Stark during the Spring '06 term at Illinois Tech.
- Spring '06