mitosis and meiosis

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  • Created by: Sarah
  • Created on: 02-06-18 10:39
what is the chiasma?
where crossing over takes place
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what are the stages of the cell cycle?
G1, G2 , Synthesis (DNA replcation), mitosis
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what is interphase?
G1 + S + G2
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How long can G1 be?
very long or permeant
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how long does it take mammlain cells to divide if they're in a proliferative state?
around 24 hours
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what cells do not divide?
differentiated cells
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what are sister chromatids?
identical copies of the maternal and paternal homologues
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what are the homologoues?
1 maternal and 1 paternal homologue
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after DNA replication what have you got?
sister chromatids (copies)
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stages of mitosis?
PMAT- prophase, metaphase, anaphase and telophase
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what happens in telophase?
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what happens in prophase?
condensation of sister chromatids need to package the DNA to be able to pull the, apart
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what happens in metaphase?
chromatids line up along the metaphase plate and are attached to the spindle. chromosomes attached to spindle by MT into kinetochore
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what happens in anaphase?
segragation of sister chromatids
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What 2 types of yeast are used to study cell cycle?
fission yeast- pombe and budding yeast- cerevisae
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how do you study cell cycle with fission yeast?
they grow out and do cell cycle in 1D so can measure them
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what are yeast good to study cell cycle with?
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why can budding (cervesiae) yeast be used?
can measure the size of bud to see how far through cell cycle
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advantages of yeast in cell cycle?
1) rapid division rate 2) never reach homeostasis always dividing 3) cell cycle genes highly conserved 4) grown as haploid or diploid
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where were cdc (cell division cycle genes) named?
in yeast so when discovered in human still carried yeast name
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why is it good to be able to grow yeast as haploid or diploid?
diploid can be heterozygous- 1 good and 1 bad copy of the gene grow up colony as diploid then make haploid to see effect of the gene
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how else can you study cell cycle genes in yeast?
1) grow as diploid and turn haploid 2) temperature sensitive mutations
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what is the principle behind temperature sensiitve mutations?
can grow up colony with permissive temp then change to restrictive temp will mutate gene and will all arrest at one stage of cell cycle
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what are checkpoints needed for in the cell cycle?
tissue size + growth also very important in cancer
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when is the start checkpoint?
endish of G1
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what is the start checkpoint checking?
is env favourable
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what is the next checkpoint after the start checkpoint?
G2/M checkpoint- between G2 and metaphase
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what is the G2/M checkpoint for?
to check all DNA is rep? is env favourable
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what is the metaphase to anaphase checkpoint for? what protein is involved here?
is all chr attached to the spindle? APC
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what is APC?
Anaphase promoting complex- ubiquitin ligase
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what is APC needed for?
to check all chrs are attached to the spindle
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what does APC ubiquitinate?
M cyclin, S cyclin, Securrin
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what does APC regulate?
E1 + E2 ubiquitination enzymes
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what subunit is needed to activate APC?
cdc20 subunit
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what is securin needed for?
securin is a protein that holds together sister chromatids when estroyed will allow anaphase to begin
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what cyclins drop at Metaphase to anaphase checkpoint?
M cyclin + S cyclin- destroyed by APC
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what is APCs function?
The APC/C's main function is to trigger the transition from metaphase to anaphase by tagging specific proteins for degradation. The three major targets for degradation by the APC/C are securin and S and M cyclins.
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what are different inputs into cdks important for?
make sure you don't begin the next phase until everythings accomplished
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what are gametes?
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what needs to be packaged into each gamete?
only 1 homologue- either maternal or paternal
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what part of meiosis is like mitosis?
meiosis 2- involves separating sister chromatids
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what happens in meiosis 1?
lining up of sister chromatids, crossing over and separate homologues
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what is separated in meiosis 1?
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what is separated in meiosis 2?
sister chromatids
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what activates cdks?
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what does wee1 kinase do?
inhibits cdks by adding an inhibitory phosphate
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what does cdc25 phosphatase do?
removes inhibitory phosphate from cdk and activates it
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what is expression of cyclins dependent on?
stage of cell cycle
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what happens when cyclins activate cdks
cdks go around phosphorylating proteins needed for that stage of the cell cycle
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what can bind to cdk to inactivate it?
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what happens in meiosis I?
duplication -> makes sister chroamtids - pair up in metaphase, crossing over + segragation of homologues
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what are the cells by the end of meisois I?
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what is the difference between meiosis II and mitosis?
both separating sister chromatids but meiosis cell is haploid whilst mitosis cell is diploid
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when do homologues pair up?
meiosis I prophase
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when homologues pair up how many copies of the chromosome do you have?
4 copies- replicated maternal and paternal chr
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what is pairing of the homologues facilitated by?
synaptonemal complex
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what is a bivalent? wgat is it needed for?
a pair of homologues chromosomes- hold maternal and paternal together allows crossing over to take place and formation of chiasma
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what is chiasma?
where crossing over takes place
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what 2 purposes does HR serve?
1) aligns chromosomes ready for anaphase + facilitates formation of synpatonmeal complex 2) allows for genetic recombination needed for genetic variation
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what is non disjunction?
where you don't have the right chormosome number
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what are gametes that arise from non disjunction called?
aneuploid- don't have the right ploidy
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how much of mammalian sperm and eggs are aneuploid?
4% sperm 20% eggs
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what does aneuploid gametes result in?
miscarriage or down syndrome
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why do we do crossing over if it's risky
evolution huge advantage
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what are xenopus used to study?
biochemical approach to cell cycle
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advantage of xenopus as cell cycle model?
rapid division, lay lots of eggs, cell free mitosis, large size- can inject inhibitors and RNA
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how do you do cell free mitosis?
take cytoplasm from eggs and sperm and ATP put in a test tube will start mitosis
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how can cell free mitosis be manipulated?
can add antibodies follow proteins or take samples at different stages eg see if phosphorylated
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Card 2


what are the stages of the cell cycle?


G1, G2 , Synthesis (DNA replcation), mitosis

Card 3


what is interphase?


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Card 4


How long can G1 be?


Preview of the front of card 4

Card 5


how long does it take mammlain cells to divide if they're in a proliferative state?


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