One - This may be one plausible scenario but why higher...

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One "story" about the origin of sex is as follows (from J. Maynard-Smith, The Evolution of Sex , Cambridge University Press, 1978): 1. Binary cell fusion (advantage ~ hybrid vigor; masking deleterious mutations) 2. Evolve the use of one spindle apparatus (advantage = maintaining both sets of chromosomes and hence any hybrid vigor effects 3. Homologous pairing and chiasma (next step but advantage unclear; generates variation but also creates regions of genetic homozygosity) 4. Reduction division + syngamy (favored to restore heterozygosity)
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Unformatted text preview: This may be one plausible scenario but why higher eukaryotes spend so much of the haploid-diplod life cycle in the diploid stage is unclear Subsequent evolution and maintenance of sex and recombination . Observation: one can select (both up and down) for rates of recombination between two loci without affecting other rates of recombination (see figure 8.6, pg.213). This means that there is genetic variation affecting recombination , which in turn means that selection can alter the rates of recombination....
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