Question

A plant species X with n=5 chromosomes was crossed with a related species Y with n = 7 chromosomes. The F1 hybrids produced only a few pollen grains, which were used to fertilize the ovules of related species Z with n=7 chromosomes. A few plants were produced from this cross, and all had 19 chromosomes. The F1 hybrids (with 19 chromosomes) were mated with related species W with n=11 chromosomes. A few plants were produced from the cross and all had 30 chromosomes. Following self-fertilization of the F1 hybrids a few F2 plants were produced, each with 60 chromosomes. These plants were phenotypically different from either of the original species and were highly fertile. (Refer to chapter 8 in your text, your notes and pay close attention to Fig. 8.28 and the associated text.) a. Explain by diagram and description the events that produced these fertile F2 hybrids. You must be specific and very clear about what is happening. Let the species designation symbolize the haploid number of chromosomes in each species. For example, X = n= 5 and XX =2n=10 and so on. b. Give the karyotype of the gametes produced by the highly fertile F2 plants. Use the species designation. For example, if the gametes were 4n, then you would write: XXYY. c. Using appropriate genetic terminology, tell what type of polyploid plant ultimately arises as a result of the above crosses.

Answer 1

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