• Exam%3%will%be%held%Friday,%Nov%13th%in%the%Tes:ng%Center%Arjona%110%• You%must%sign%up%for%an%available%Ex am%Slot%on%HuskyCT%Exam%Registra:on%Link!%!• Exam%slots:%12:00-1:30,%1:30-3:00,%3:00-4:30,%4:30-6:00;%there%is%no%regular%class%on%exam%day.%• If%you%have%another%class%conflict%w ith%the%available%slots%you%must%provide%a%scr eenshot%of%your%UConn%schedule,%and%contact%me%ASAP!%• HuskyCT%Materials%will%be%unavailable%online%on%Friday.%Be%sure%to%download%any%materials%you%want%if%you%plan%on%last%minute%studying!%%• There%will%be%2%Review%sessions%before%the%Exam.!• 1.!Wednesday,!11/11,!6-8pm!TLS!154!• 2.!Thursday,!11/12,!6-8pm!TLS!154!• Bring!your!Problem!Sets!!• The%early%exam%for%people%with%legi:mate%reasons%that%have%been%cleared%with%me%will%be%on%Thursday,%11/12,%:me/place%TBA.%• If!you!need!to!take!the!early!exam!for!a!legiGmate!reason!and!have!NOT!contacted!me!yet,[email protected]!• Students%who%have%CSD%Exam%:me/place%accommoda:ons%will%be%taking%the%exam%at%the%CSD%office.!Please!get!any!Exam!AdministraGon!Forms!to!me!ASAP.!Mitosis%(Part%I):%Prophase,%Pro-Metaphase,%Metaphase%%%%hMp://www.youtube.com/watch?v=RYip2_ex070!Coordinated%mitosis%in%fly%embryos!Last%Class:%%Cytoskeletal%Func:ons%in%Interphase!Microtubules%in%a%radial%array%(Cytokinesis)%Ac:n%1. Membrane!Protrusion(Lamellipodia!&!Filopodia)!2. Cell!Adhesion!!!!!!!!!!!!!!!!!!!!!!!!!(Stress!Fibers!&!Focal!Adhesions)!3. Endocytosis!and!Trafficking!!!!!(Clathrin!Pits!&!Endosomes)!4. Cytokinesis!à!Later!!Microtubules%1. Organelle!PosiGoning! !!!!!!!!!!!(ER!&!Golgi)!2. Anterograde!Transport!!!!!!!!!!!!!!(ER-Golgi-Plasma!Membrane)!3. Retrograde!Transport!!!!!!!(Endosome-Golgi)!4. Mitosis!à!Later!(now!)!Today:%%Mitosis!Figure 17-4 Molecular Biology of the Cell (© Garland Science 2008) Mitosis!is!the!process!of!chromosome!segregaGon.!M%phase%occupies!a!small!fracGon!of!the!cell!cycle.!The!rest!of!the!cell!cycle!is!called!interphase!and!consists!of!three!phases.!(1)!G1%phase!(Gap!1)!is!the!period!between!the!compleGon!of!the!previous!mitosis!and!the!iniGaGon!of!DNA!synthesis!for!the!next!mitosis.!(2)!S%phase%is!the!period!of!DNA!synthesis!for!chromosome!duplicaGon!and!(3)!G2%phase%(Gap!2)!is!the!period!between!the!compleGon!of!DNA!replicaGon!and!the!iniGaGon!of!mitosis.!Figure 17-3 Molecular Biology of the Cell (© Garland Science 2008) (1)!Chromosome%condensa:on.!This!is!required!for!the!organized!segregaGon!of!chromosomes!to!daughter!cells.!Condensed!chromosomal!DNA!is!organized!into!nucleosomes!by!histones!and!is!further!compacted!by!proteins!known!as!condensins!in!M!phase.!(2)!Mito:c%spindle%assembly.!The!mitoGc!spindle!aligns!the!replicated!chromosomes!in!a!plane!that!bisects!the!cell.!Each!chromosome!then!separates!into!two!daughter!chromosomes,!which!are!moved!by!the!spindle!microtubules!to!opposite!spindle!poles.!(3)!Forma:on%of%the%contrac:le%ring.!This!structure!consists!of!acGn!filaments!and!myosin!II!assembled!beneath!the!plasma!membrane!at!the!equator!of!the!dividing!cell.!As!cells!exit!mitosis,!ring!contracGon!pulls!the!membrane!inwards!and!divides!the!cell!in!two.!M%phase%features%3%major%subcellular%changes%!G1%G2%S%D.Drubin!An%overview%of%the%stages%of%mitosis!M%is%visible%Kinetochores%begin%to%assemble%In!condensed!chromosomes,!sister!chromaGds!are!aMached!to!each!other%at!the!centromere,!a!specific!region!of!the!chromosome!that!can!be!recognized!by!a!constricGon!of!close!chromaGd!aMachment.!In!some!organisms,!the!centromere!is!determined!by!specific!genomic!DNA!sequences,!in!others!(many)!it!is!defined!epigeneGcally.!!Mitosis%builds%on%the%events%of%S-phase%and%G2!Ager!S!phase,!each!duplicated!chromosome!contains!two%sister%chroma:ds,!each!consisGng!of!a!single!linear!piece!of!DNA!that!is!extremely!long.!To!properly!segregate!the!genome,!DNA!must!be!condensed!into!compacted!structures!that!will!not!break!during!segregaGon.!Chromosome!condensaGon!involves!a!set!of!ATPases!called!condensins!that!work!together!with!topoisomerases!to!drive!DNA!supercoiling!and!compacGng.!This!begins!at!the!end!of!G2.!D.Drubin!Sister!chromaGds!need!to!sGck!to!one!another!during!the!iniGal!stages!of!mitosis.!Cohesion!is!mediated!by!proteins!called!cohesins!that!‘glue’!the!sisters!together.!(To!separate!the!sisters,!cohesins!get!degraded.)!!Specialized!protein!complexes!called!kinetochores!eventually!assemble!on!the!centromere!of!each!sister!chromaGd!facing!out!in!opposite!direcGons.!And!they!aMach!to!microtubules,!as!we!will!see!later.!Mitosis!also!ogen!depends!on!duplicaGon!of!the!centrosome.!(Remember,!the!centrosome!is!the!principal!microtubule!organizing!center!(MTOC)!in!animal!cells.!It!consists!of!two!centrioles!surrounded!by!pericentriolar!material!that!nucleates!MT!assembly.)!!At!the!beginning!of!G1,!the!cell!has!1!centrosome.!During!the!rest!of!interphase,!the!centrioles!and!centrosome!components!are!duplicated!but!remain!together!at!one!side!of!the!nucleus.%The%G2-to-M%transi:on%is%gradual!Figure 17-31 Molecular Biology of the Cell (© Garland Science 2008)1-%Prophase!Prophase!begins!when!condensed!chromosomes!can!be!seen!by!light!microscopy.!Also!in!prophase,!interphase!MTs!disassemble,!the!two!centrosomes!separate,!and!each!centrosome!nucleates!a!radial!array!of!MTs!called!an!aster.!The!two!asters!move!apart!to!opposite!sides!of!the!nucleus!to!begin!forming!the!mitoGc!spindle.!!The%forma:on%of%the%mito:c%spindle%will%involve%the%organiza:onal%ac:vity%of:%(1)%centrosomes%and%(2)%chromosome
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