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25 Cards in this Set
- Front
- Back
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Cel cycle
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contents of cell must be duplicated before dividing
contents must be distributed into two physically separate cells |
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Why are these topics important?
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-key mechanisms underlying the inheritance of all phenotypic traits
-mitosis= critical for embroynic development, wound healing -meiosis= increases genetic variation -meiosis= allows us to identify the genes underlying traits -problems with these two = cancer and defects |
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Cell division in Eubacteria and Eukaryotes
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Eubacteria: no nucleus, one chromo, no organelles
(simpler process overall) Eukaryotes: nucleus surrounds the genetic material, multiple chormos need to be segregated correctly, organelles need to be replciated, and control of division is crucial |
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steps of cell division in eubacteria
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cell grows, dna is replicated, and then divided when the rigng around middle tightens and splits apart
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Eukaryotic cell cycle
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Interphase: time between mitoses
-G1= cell growth -S= dna replication -G2=preparation for mitosis mitosis: once cell separates into two |
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Mitosis
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THIS STEP HAS TO BE PERFECT
-perfect segreattion of chromosomes and centrioles -two cells produced, each diploid |
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Overview of Mitosis
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prophase, metaphase, anaphase, telophase, and cytokinesis
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Duplication of Centrioles
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each cell has one centriole pair
centrioles become poles of spindle during mitosis |
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Division of Mito
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Own genome. dont have S phase. they have circular dna and are decendents of bacteria
-several copies of mito dna -replication happens whenver -not tied to physical division -protein dnm1= makes a laso that pinches middle out -hydrolisis of GTP-GDP squeezes even more |
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Chromosome Segregation
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one from sperm, one from egg.
s phase each is copied= sister chromatids then these segragate during mitosis 4 Processes Ensure this: -association and condensation of sister chromatids -attachement of chromatid pairs to spindle -separatioin of sister chromatids -cytokineses into 2 cells |
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Chromosome pairing and condensing
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1. long stretches of interwould alpha helixes (can open or close)
-top is hinge, and attached to openeing is a motor protein= hyrolzie atp and can spring it open or closed 2. either a CAP/ SCC protein regulates when it is open or clsed, recieve infor from cells that control cell cycle |
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Cohesions
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attach sister chromatins during S phase. separate. chohensions are coming around them and clamping daughter strand, hugging the whole length of dna molecule. S phase over, then they are stitched together and held in cohesion.
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Condensins
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Help chromatin condense= prophase
-open and grab loops of chromosomes -stabalizes loops |
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Attachement of sister chromatins
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Cohesions wrap around, ssc is regulatonry. kinesan will put them together, and scc clamps on= stitch them together one end to another
a few cohesions remain following condensation. once ready to separate have to break that= separase then cleaves complex at anaphase allowing separation come ON during S phase, come OFF during anaphase |
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Mitotic Spindles
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composed of many microtubles
pull apart sister chromatids provide framework for movements during mitosis |
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Centrioles organize the spindle
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anchor the microtubles
-astral: spray out all different directions -polar: directed towards center and overlap with those from other sides -kinetochore: attach to chromosomes: pole to chromo |
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Kinetochore
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OPPOSITE DIRECTIONS
-where chromatids attach to mitotic spindle -link chromatin proteins to microtubules -multiple microtubules attach to each kinetochore On right side, all non covalent bonds that lock together On left side, reach out and interact to grab onto microtubule |
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Motor proteins that power mitosis
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They walk in a specific direction along microtubules
Kinectochore: motor domain carries cargo domain to positive end Polar: motor movement towards plus end whle the top is going the opposite direction : moves the centrioles apart Astral: motor movement to minus end on cortex |
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How do the microtubules move away metaphase plate?
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depends on stablilty of structure; tubulin is small and makes dimers between alpha and beta forms= heterodimer
- attache either GTP or GDP to beta subunit, while GTP ismore stable + end grows with addition of subunits= more stable - end shrinks with loss of same length= balance between gain and loss - end attaches to centrioles, while + end faces out |
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how do microtubulins move chromosomes ?
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+ end is polymerization, - is depolymerization
-kinetochore proteins switch between these -k-1 protein promotes the depolymerizatoin at + end because they need to be plucked away to make room gets shorter and shorter as more leave and less come in |
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Metaphase- anaphase transition
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when you reach metaphase, starts to move apart
make sure all the chromo are there and attached= they are being pulled on by both poles -chromatid pairs are condensed, kintetocores attach -cohesions broken down by separase, - kinetichores bring to one pole or the other |
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Cytokinesis
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cell pinches off into two
ring of actin and miosin slide past each other, shrink distance, and band and contract pinching them off |
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Meiosis
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One cell (2n)--> one cell (4n) during S phase when each is replicated
First cell division is special: genetic material shuffled and recombined between two sister chromatids cells divide= SISTER CHROMATIDS DONT SEPARATE. back to 2n-- divide again -sister chromatds separate, get 4 different cells non identical |
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Kinetochores during Meiosis I
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Same direction
during Mitosis and meiosis 2: separate sister chromatids -Meiosis 1 separates maternal from paternal chromatid pairs |
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Genetic Diversity
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Recombination: partial exchange of info between sister chromatids= unique combo of allels
Independent assortment: random segregation of chromatids to each gamete; unique combo of chromatids BOTH DURING MEIOSIS 1 |
