BIO 370 Chapter Notes - Chapter 16: Linkage Disequilibrium, Theodosius Dobzhansky, Reproductive Isolation
Reproductive Isolation via Chromosomal Rearrangement
What are the major types of chromosomal rearrangements?
• Fusion
• Fission
• Inversions
• Translocations
• The first two, ad the latter, whe huks are large ad/or ualaed, lead to
problems in meiosis.
When some individuals in a population possess the original chromosome arrangement and
others have the rearranged chromosome set, what do you think might be the result if they
hybridize?
Linkage disequilibrium in descendants.
Carrying it a bit further, when individuals in one population have the original chromosome
arrangement and individuals in another population have the rearranged version, what do you
think might happen between the two populations?
Reproductive isolation.
Reproductive Isolation via Dobzhansky-Muller Incompatibility
Dobzhansky and Muller independently developed a conceptual model of how hybrid
incompatibility, and hence postmating reproductive isolation, might evolve as a result of
epistasis (effects of one gene modified by another).
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Document Summary
What are the major types of chromosomal rearrangements: fusion, fission, translocations, the first two, a(cid:374)d the latter, whe(cid:374) (cid:862)(cid:272)hu(cid:374)ks(cid:863) are large a(cid:374)d/or u(cid:374)(cid:271)ala(cid:374)(cid:272)ed, lead to. Dobzhansky and muller independently developed a conceptual model of how hybrid incompatibility, and hence postmating reproductive isolation, might evolve as a result of epistasis (effects of one gene modified by another). Epistatis interactions b/w a and b loci fitness costs to individuals with both a2 and b2 alleles = hybrids are selected against, est. reproductive isolation b/w pop 1 and 2. The bottom line is this: if there are epistatic interactions between loci, there may be fitness costs associated with those combinations. Negative epistasis between alleles of two loci can lead to reduced fitness in the hybrids, and this in turn can select for mechanisms of reproductive isolation between the populations. Haldane suggested that sex chromosomes may play a special role in the genetics of reproductive isolation.
