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Meiosis and Sexual Life Cycle

Meiosis and Sexual Life Cycle. An Introduction to Heredity Role of Meiosis Origins of Genetic Variations. Offspring acquire genes from parents by inheriting chromosomes DNA, genes and chromosomes Locus-location of a gene. Asexual vs Sexual 1) Number of parents 2) haploid vs. diploid

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Meiosis and Sexual Life Cycle

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  1. Meiosis and Sexual Life Cycle An Introduction to Heredity Role of Meiosis Origins of Genetic Variations

  2. Offspring acquire genes from parents by inheriting chromosomes DNA, genes and chromosomes Locus-location of a gene Asexual vs Sexual 1) Number of parents 2) haploid vs. diploid 3) clone vs. variations An Introduction to Heredity

  3. Role of Meiosis • Alternation of fertilization and meiosis • Karyotype • Homologous chromosomes (homologues) • Autosomes • Sex Chromosomes • Cell types 1) somatic cells (2n) 2) germ cells (1n)

  4. Variety of Sexual Life Cycles • Animal-gametes are the only haploid cells • Fungi-zygote is the only diploid cell • Plants-alternate between a multicellular haploid and diploid stage

  5. Meiosis • Solves the problem created by sexual reproduction • 2n1n • 4 cells • Gametes are not clones • Two stages meiosis I and meiosis II

  6. Meiosis I • Interphase I- • Prophase I-synapsis occurs; tetrad forms; crossing-over occurs • Metaphase I • Anaphase I-sister chromatids remain attached • Telophase I

  7. Meiosis II • Interphase II- No S phase • Prophase II • Metaphase II-chromatids separate • Anaphase II • Telophase II-four haploid cells

  8. Origins of Genetic Variations • Independent assortment • Crossing-over • Random fertilization

  9. Evolutionary Adaptation Depends on Population’s Genetic Variations • Variations + environmental change  adaptation? • Two sources of variations 1) sexual reproduction 2) mutation

  10. Videos and Websites • http://www.youtube.com/watch?v=D1_-mQS_FZ0 • http://www.youtube.com/watch?v=eaf4j19_3Zg • http://www.biology.arizona.edu/cell_bio/tutorials/meiosis/main.html

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