Origin of Sex - • synaptonemal complex may have evolved...

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Origin of Sex asexual reproduction - creates genetically identical offspring all chromosomes from a single parent animal asexual reproduction involves budding off of a mass of cells parthenogenesis - development of an adult from an unfertilized egg o common form of reproduction in arthropods o diploid female bees, haploid male bees more advantageous than sexual reproduction (recombination does more harm than good in evolution) sexual reproduction - multiple theories on its origin no other process makes diversity more quickly, speeds up evolution asexually reproducing organisms tend to live in isolated, demanding habitats where natural selection doesn’t favor change sexually reproducing organisms tend to favor versatility, best supported by genetic recombination DNA repair hypothesis - diploid cells can repair chromosome damage protists only use sexual reproduction in times of stress
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Unformatted text preview: • synaptonemal complex may have evolved as a way to fix double-stranded DNA damage • undamaged homologous chromosome used as template to fix damaged DNA contagion hypothesis- mobile genetic elements infected eukaryotes • elements w/ genes for fusion w/ uninfected cells and synapsis can quickly copy itself onto homologous chromosomes • idiomorph- genes in homologous positions on chromosomes but are so different that they can’t be of homologous origin • explains the mating type “alleles” in fungi red queen hypothesis- saves recessive alleles useful in the future • keeping alleles allow organism to keep up w/ changing environment • sexual species can’t get completely rid of recessive traits in heterozygotes Muller’s ratchet- can keep mutation level down • asexual populations can’t get rid of mutations • sexual populations get rid of mutations through natural selection...
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