Chapter 13 Notes MEIOSIS

Fromonepole thoseoftheotherhomologareadachedto

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Unformatted text preview: microtubules! from!one!pole! ! Those!of!the!other!homolog!are!aDached!to! microtubules!from!the!opposite!pole! Meiosis(I:((Separa;on(of(Homologous(Chromosomes( Meiosis 1: Split into 2 daughter cells Anaphase(I:( Telophase(I:( Breakdown!of!proteins! responsible!for!cohesion! along!sister!chroma8d! arms!allows!homologs!to! separate! ! *! Homologs move towards OPPOSITE POLES guided ! by spindle apparatus ! ! ! Sister!chroma8d!cohesion! persists!at!the!centromere! causing!sister!chroma8ds! to!move!as!a!unit!towards! the!same!pole! At!the!beginning!of! telophase!I,!each!half!of!the! cell!has!a!complete!haploid! set!of!replicated! chromosomes!!! ! *! Each chromosome composed of ! two sister chromatids .!!! ( Note:!!sister!chroma8d!are! not!iden8cal!due!to! crossover!that!occurred!in! Prophase!I! ! Cytokinesis!occurs! simultaneously!with! telophase!I,!forming!two! daughter!cells! ! Meiosis(II:((Separa;on(of(sister(chroma;ds( Prophase(II( Metaphase(II( Spindle!apparatus!forms! ! Chromosomes!(s8ll! composed!of!two!sister! chroma8d!associated!at! the!centromer)!move! towards!metaphase!II! plate! ! *! chromosomes are aligned on ! metaphase plate as in mitosis ! ! The!kinetochores!of!the! sister!chroma8ds!are! aDached!to!microtubules! extending!from!opposite! poles! ! Meiosis(II:((Separa;on(of(sister(chroma;ds( Each daughter cell from Meiosis I splits, forming 4 cells altogether Anaphase(II( Breakdown!of!protein! holding!sister!chroma8ds! together!at!centromere! allows!the!chroma8ds!to! separate.! ! ! *! Chromatids now move towards opposite poles as INDIVIDUAL chromosomes cohesion lost at centromere! Telophase(II(and( Cytokinesis( Nuclei!form,!the! chromosomes!begin!to! decondense,!and! cytokinesis!occurs! ! One!parent!produces!four! gene8cally!different! daughter!cells!! GENETIC VARIABILITY - 4 different daughter cells! Here, CROSSING OVER occurs! start out with 6 chromosomes! 2 daughter cells that are HAPLOID (half the # of chromo somes as parents) 2 daughter cells that have the same chromosomes as parent NO GENETIC VARIABILITY....
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