BIOLOGY 1M03 Lecture Notes - Lecture 7: Sister Chromatids, Hybrid Zone, Reproductive Isolation
12 Oct 2016
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In plants, somatic cells that have undergone many mitosis rounds can undergo meiosis and produce gametes. If sister chromatids separate during anaphase but fail to migrate to opposite poles (during mitosis), then the result can be a tetraploid daughter cell that later undergoes meiosis to form diploid gametes. The ability by some plants to self-fertilize makes it possible for diploid gametes to fuse and create genetically isolated tetraploid populations. Hybridization between plant species is common, creating opportunities for speciation via allopolyploid formation. In summary, speciation by polyploidization is driven by chromosome-level mutations and occurs in sympatry. Compared to gradual speciation by geographic isolation or by disruptive selection in sympatry, speciation by polyploidy effectively is instantaneous. Speciation by polyploidization is fast, sympatric, and common. What happens when isolated populations come back into contact depends on many factors but most importantly on whether the populations have diverged genetically. When zygotes can form, populations may successfully interbreed.
