11-04-17 Exam 3 Notes.docx - Chapter 11 Sexual reproduction...

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Chapter 11Sexual reproduction is the merging of the genetic contribution of two cells from different individualsSexual Life Cycle: meiosis and fertilization, diploid cells (somatic cells of adults have 2 sets of chromosomes), Haploid cells (gametes have only 1 set of chromosomes), offspring inherit genetic material from 2 parentsHaploid sperm and haploid egg fertilize to diploid zygote w/ paternal and maternal homologueIn most animals diploid state dominates (zygote first undergoes mitosis to produce diploid cells, later some diploids undergo meiosis to produce haploid gametes, germ-line cells undergo meiosis to produce gametes)Meiosis: 2 rounds of division, Meiosis I and II, each has Prophase, Metaphase, Anaphase, and TelophaseSynapsis: during early Prophase I, homologous chromosomes become closely associated, includes formation of synaptonemalcomplexes (aka tetrad or bivalents)First division is called reduction division (results in daughter cells that contain 1 homologue from each chromo pair), no DNArepl. Between meiotic divisions, 2nddivision does not further reduce the number of chromo (separates sister chromatids for each homologue)Meiosis: Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II (Interphase period similar to mitosis w/ G1, S, and G2 phases) (Following interphase Germ-Line cells enter Meiosis I)Chromosomes (A paternal and maternal chromatid stacks are called homologues, when bound during Meiosis I the two chromatids that match are called sister chromatids. The center that binds the sister chromatids is the Centromere and the Kinetochore is the middle of the Chromatids, what binds the sister chromatids on another sister chromatid is Synaptonemal ComplexProphase I: Chromo coil tighter, become visible, nuclear envelope disappears, spindle forms, Chromo are 2 sis. Chromatids, Synapsis (homo become close, crossing over occurs between non-sister chromatids, attached at chiasmata (which move to end of chromo arm before metaphase I))Crossing Over: Exchange of material between chromatids, Chiasmata is the crossing over site and contact maintains until Anaphase IMetaphase I: Terminal chiasmata holds homo after cross over, microtubules from opposite poles attach to each homo, aligned at metaphase plate side-by-side, orientation of each pair of homo on the spindle is randomAnaphase I: Micro tubes of spindle shorten, Chiasmata breaks, homo separate from each other and move to opposite poles, Sister Chromatids remain attached at centromeres, Each pole has complete haploid set of chromo consisting of 1 member of each homo pair, independent assortment of maternal and paternal chromoTelophase I: Nuclear envelope reforms around daughter nucleus, sister chromatids no longer identical due to Prophase Icross over, Cytokinesis may or may not occur after Telophase I, Meiosis II occurs after interval of variable lengthMeiosis II: resembles a mitotic division, Prophase II nuclear envelopes dissolve and spindle apparatus forms, Metaphase II

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