BIOLOGY 1M03 Lecture Notes - Lecture 12: Mitosis, Reproductive Isolation, Disruptive Selection

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If populations become isolated, it is unlikely that mutation, by itself, could cause them to diverge appreciably. Mutation, however, that results in polyploidy - containing more than two chromosomes sets - can cause speciation, particularly in plants. For example, tetraploid individuals are isolated genetically from wild- type diploid individuals because they produce diploid gametes rather than haploid gametes (i. e. , a mutation eliminates gene flow between normal and mutant individuals). If two gametes combined, the resulting zygote would be triploid. Triploid individuals produce gametes with dysfunctional chromosome sets. Triploid organisms are infertile, which can be prized by humans (e. g. , seedless fruit). Mutations that result in chromosome number doubling produce autopolyploid individuals. In them, the chromosomes all come from the same species. Allopolyploid individuals are created when parents that belong to different species produce an offspring in which chromosome number doubles. Researchers found a tetraploid (4n) maidenhair fern population.

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