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Chapter 13 Notes MEIOSIS

Cellsareusuallygene8cally iden8calexcep8onmuta8on sex

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Unformatted text preview: ry(Fission( Daughter!cells!are!usually!gene8cally! iden8cal!(excep8on!–!muta8on)! SEX CELLS (GAMETES) HAVE 23 CHROMOSOMES! AUTOSOMAL CELLS HAVE 46. Sexual(Reproduc8on(( *! Gametes are genetically DIFFERENT from each other ! AND the parents Gametes!have!half!the!number!of!chromosomes! Overview(of(Meiosis:((Reduc;on(division( ! Red!chromosome!from!female!parent! Blue!chromosome!from!male!parent! attached by cohesin molecules *! Diploid cell with replicated chromosomes Homologous! chromosomes! separate! cohesin molecules separated at ARMS here No!replica8on!of!chromosomes!between! Meiosis!I!and!Meiosis!II! Sister!chroma8ds! separate! *! *! One gamete gets one of the homologs and the other gets the other one now you have a HAPLOID cell w/ replicated chromosomes! now cohesin molecules completely separate Now you have HAPLOID cell wi/ UNREPLICATED chromosomes Meiosis(I:((Separa;on(of(Homologous(Chromosomes( Prophase(I( Chromosomes!begin!to!condense!and!homologous! chromosomes!align!–!gene!by!gene! ! Crossover between NONSISTER chromatid of homologs *!takes plae while homologs are in synapsis. (where they cross ! over is called a CHIASMATA) - this is important - if no crossing over occurs, they can't move around as pairs - it attaches them! ! Synapsis!ends!in!midVprophase!and!chromosomes!move! apart!slightly! ! Each!homologous!pair!has!one!or!more!chiasmata!–! points!where!crossover!has!occurred!! ! *! Homologs are still associated due to sister chromatid cohesion ! Centrosome!movement,!spindle!forma8on,!and!nuclear! envelope!breakdown!occur!as!in!mitosis! ! Homologous!pairs!move!towards!metaphase!plate! In!late!prophase!I,!microtubules!from!one!pole!or!the!other!aDach!to!the!two!kinetochores!at!the! centromere!of!the!two!homologs! ! Meiosis(I:((Separa;on(of(Homologous(Chromosomes( Metaphase(I( Pairs!of!homologous!chromosomes!are! arranged!on!the!metaphase!plate!with!one! chromosome!in!each!pair!facing!each!pole! ! Both!chroma8ds!of!one!homolog!are! aDached!to!the!kinetochore!...
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