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Block Two Cell Bio > Mitosis and Meiosis > Flashcards

Mitosis and Meiosis Flashcards

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Biology 101 flashcards
1
Q

Mitosis

A

take diploid parent cell and make 2 identical diploid daughter cells; interphase and M phase; mitosis refers to the division of the nucleus

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2
Q

interphase

A

includes S phase and DNA replication where you get an exact copy of each

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3
Q

M phase

A

chromosome separation and cytokenesis (division of the cytoplasm) (mitosis is 2 parts one is mitosis or division of nucleus the other is cytokenisis or division of cytoplasm

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4
Q

cell cycle driven by

A

Cdk - cyclin dependent kinase; promotes cell cycle progression by phosphorylating specific kinases at different stages of cell cycle; protein kinases have associated cyclin subunits required for cyclin activity; cyclin subunits regulated at protein stability level

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5
Q

Stages of mitosis

A
  1. Prophase
  2. Pro-metaphase
  3. Metaphase
  4. Anaphse
  5. Telophase
  6. Interphase (rest of cell cycle)
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6
Q

Prophase

A
  • chromosomes condense
  • centrosomes migrate to poles
  • spindle starts to form outside nucleus
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7
Q

Pro-metaphase

A
  • nuclear envelope breaks dow; initiated by Cdk-mediated phosphorylation of lamins
  • chromsomes attach to spindle
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8
Q

Metaphase

A
  • sister chromatids become linked to opposite spindle poles

- chromosomes align at equatorial plane

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9
Q

Anaphase

A
  • sister chromatids separate

- Daughter chromosomes are pulled to opposite ends of the cell

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10
Q

Telophase

A
  • chromosomes arise at poles
  • nuclear membrane reforms
  • chromsomes decondense
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11
Q

cytokenesis

A

division of cytoplasm via contractile ring composed of actin and myosin which forms in same plane as metaphase plate inside of plasma membrane; starts during anaphase ends completed by end of telophase

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12
Q

Interphase

A

rest of cell cycle; consists of G1 (Gap 1 where cell commits to new round of cell division), S (where genome is duplicated), and G2 (Gap 2 where cell prepares to divide)

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13
Q

centrosome

A

microtubule organizing center; each contains a pair of centrioles; replicate during interphase, move poles during prophase

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14
Q

centrosome cycle

A

each cell starts with one centrosome, at G1 it replicates, at prophase centrosomes separate, nucleate spindle, each daughter cell inherits one centrosome

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15
Q

cohesion

A

deposited during DNA replication, holds sister chromatids together; these are dissolved during anaphase allowing chromatids to separate and migrate to opposite ends of the cell

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16
Q

Condensin

A

promotes DNA coiling; 50 fold condensing during prophase

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17
Q

separase

A

enzyme that promotes separation of chromatids by cleaving a component of cohesion complex; this acts between metaphase and anaphase in mitosis and metaphase I and anaphase I and metaphase II and anaphase II in meiosis

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18
Q

securin

A

prior to anaphase separase exists in inactive state with securin

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19
Q

anaphase promoting complex

A

APC: this is activated by Cdk during anaphase, this induces cleaving of securing which frees separase which promotes separation of chromatids by cleaving a component oc cohesion complex; this will not start until all of the chromosomes are properly attached to the spindle

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20
Q

chromosome separation

A
  1. kinetochore microtubules shorten which drags attached chromatid toward core
  2. spindle poles themselves further separate pulling chromatids farther apart via motor proteins that overlap microtubules and outward force exerted by astral microtubules
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21
Q

kinetochore microtubule

A

link spindle pole to chromosomes via kinetochore (protein complex that forms at centromere); kinetochore assembles during prophase

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22
Q

Overlap microtubule

A

aka polar microtubules; give spindle its symmetrical bipolar shape; act in pole separation; also called polar microtubule

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23
Q

Astral microtubule

A

radiate out from centrosome; act in pole separation and spindle positioning

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24
Q

chromosome attachment to spindle

A

made possible by nuclear envelope breakdown, point of attachment is centromere which is a heterochromatic region with repeats of DNA (alpha satellite repeats every 175 nucleotides)

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25
Q

proper spindle alignment

A

should have bipolar attachment with 2 sister chromatids attaching to kinetochore to each pole this leads to tension between centromeres indicating stable attachment, anaphase doesnt begin unless chromosomes properly attached, can end up with 2 chromatids attaching to same pole, kinetochore attached to both poles, attachment of only 1 kinetocore; if one of these goes on get aniploidy

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26
Q

aniploidy

A

gain or loss of chromosome that should be in cell and isn’t due to spindle alignment issue

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27
Q

metaphase to anaphase transition

A

metaphase sister chromatids lined up on spindle, anaphase they start moving to daughter cells

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28
Q

microtubules fixed in

A

state of dynamic instability which puts chromosome under tension and poles pull in opposite directions creating tension

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29
Q

spindle checkpoint

A

ensures that APC is active only if chromosome alignment is correct otherwise APC is kept off

30
Q

sister chromatid separation

A

spindle checkpoint says ok everything in right place APC activated, APC cleaves securin which activates separase which cleaves component of cohesion complex so now sister chromatids are separated from each other and can separate (no kinetochore yet)

31
Q

Meiosis

A

process by which haploid gametes are made from diploid parent cell via 2 successive rounds of chromosome segregation in absence of intervening DNA replication

32
Q

meiosis genetic diversity

A

get genetic diversity because independent assortment of maternal with paternal so you get mixed genetic patterns also get DNA recombination between maternal and paternal copies

33
Q

Meiosis I

A
  • duplicated homologous pair
  • at least 1 cross over per pair
  • homologs align on spindle; crossover allows them to properly align on spindle
  • homologs segregate to opposite pole
34
Q

Meiosis II

A
  • spindle re-forms
  • chromosomes align
  • chromatids segregate to opposite poles
35
Q

Prophase I

A

occupies up to 90% meiotic cycle; involves pairing of homologous choromosomes (related but not identical in sequence- one maternal one paternal); recombination occurs during prophase I allowing proper chromosome segregation and also ensuring genetic diversity; protein complexes are established between homologues, lateral elements and transverse filaments form on individual chromosome, homologs align, axial (central) elements form; Leptotene, zygotene, pachytene, diplotene, diakenesis

36
Q

chiasmata

A

during prophase I recombined non sister chromatids become linked through chiasmata which hold homologs together until anaphase and ensure that one homologue segregates to each pole

37
Q

Leptotene

A

paired chromatids condense

38
Q

zygotene

A

synaptonemal complex develops

39
Q

pachytene

A

recombination occurs between non sister chromatids;
- recombination occurs at recombination nodules which are large protein complexes containing recombinant proteins; typically each chromosome goes through 2-3 cross overs

40
Q

diplotene

A

synaptonemal complex is disassembled, cross overs maintained

41
Q

diakenesis

A

Transition to metaphase I

42
Q

synaptoterminal complex

A

holds sister chromatids together while DNA recombination occurring

43
Q

hot spots

A

in genome where cross over occurs

44
Q

homologous recombination

A

genetic exchange between 2 homologous sequences

  1. Helices break and rejoin with opposite partner
  2. Site of exchange can be anywhere
  3. Heteroduplex DNA forms at site of exchange
  4. Process is highly precise
45
Q

meoitic recombination

A
  1. Formation of double stranded DNA break
  2. break resected to produce 3’ overhang
  3. protruding 3’ end invades one of homologus chromatids
  4. double holiday junction forms
  5. resolvase cuts the joined molecules and produce two recombined chromosomes; may get rejoined in such a way that there isn’t cross over
46
Q

structure of paired homologues following a cross over

A

-crossing over occurs between non-sister chromatids (any 2). resulting connections = chiastama; homologs remain linked together after crossing over bc cohesions keeping sister chromatids linked together

47
Q

non-disjunctoin

A

failure of chromosomes to separate or segregate properly at anaphase I or II can lead to Down syndrome

48
Q

meiosis I and meiosis II and poles

A

Meiosis I one homolog to each pole (sister kinetochores act as one unit); cohesions at arms dissolved but sister chromatids still held together at centromere, Meiosis II one sister chromatid to each pole (remaining centromeric cohesions dissolved and kinetochores attach to each pole and pull apart)

49
Q

metazoan life cycle

A

gamete -> fetalizatoin -> diploid cell ->zygote -> mitosis ->proliferation development -> soma -> meiosis -> haploid state

50
Q

Oogenesis

A
  1. prenatal mitotic proliferation
  2. oocytes enter meiosis and arrest, arrest can last for YEARS
  3. With stimulus oocyte will mature, (chromosomes recondense,NE breakdown, chromosome segregation)
  4. Chromatids segregate at MII (get one mature egg and one polar body)
    egg: non-motile, protected, nutrient rich
51
Q

spermatogenesis

A

meiosis initiates after puberty and then goes continuously; sperm: highly motile, stream lined, exploit maternal investment; structure of testis linked to meiosis goes from periphery of testis to inside

52
Q

Meiosis v mitosis location

A

meoisis- germ cells

mitosis- somatic cells

53
Q

meiosis vs mitosis end product

A

meiosis 1 parent cell -> 4 gametes

mitosis 1 parent cell -> 2 daughter cells

54
Q

chromosome number mitosis v meiosis

A

mitosis chromosome number maintained

meiosis chromosome number halved

55
Q

meiosis v mitosis s

A

meiosis- 1 s per 2 division

mitosis- 1 s per division

56
Q

meiosis vs mitosis chromatid division

A

meiosis- sister chromatids don’t divide at anaphase I but do at anaphase II
Mitosis- sister chromatids divide at anaphase

57
Q

meiosis vs mitosis homologs

A

mitosis- normally no pairing of homologs

meiosis- full synapsis of homologs

58
Q

meiosis vs mitosis crossing over

A

meiosis- at least one cross-over per homologous pair

mitosis- normally no crossing over

59
Q

meiosis vs mitosis variance

A

meiosis- promotes genetic variance

mitosis- conservative process

60
Q

Meiosis

A 
Prophase I
Metaphase I
Anaphase I
Telophase I
Brief interphase after meiosis I
Prophase II
Metaphase II
Anaphase II
Telophase II
cytogenesis
61
Q

metaphase I

A

bivalents (the complex of 4 chromatids) held together by chiasma, align at equatorial plate

62
Q

anaphase I

A

chiasma are resolved and cohesions at chromatid arms dissolved, sister chromatids stay attached at centromere ; homologs segregate to opposite poles

63
Q

telophase I

A

chromosomes dissociate from the spindle; nuclear membranes reform around daughter nuclei, chromosomes may decondense somewhat

64
Q

prophase II

A

nuclear envelope breaks down and chromosomes attach to newly formed spindle

65
Q

metaphase II

A

chromsomes align on equatorial plane

66
Q

Anaphase II

A

attachments between sister

67
Q

cytokenesis after telophase II

A

produces 4 haploid cells each of which contains single copy of every chromosome

68
Q

cytokenesis after telophase II

A

produces 4 haploid cells each of which contains single copy of every chromosome

69
Q

meiotic recombination

A

occurs between non sister chromatids from homologous chromosomes during prophase of meiosis I; result is reciprocal exchange of DNA between involved maternal and paternal chromatids

70
Q

heteroduplex DNA

A

formed at site of exchange (meiotic recombination); one strand from one chromosome pairs with one strand of homologous chromosome

71
Q

distance between loci

A

affects likelyhood of recombination, closer 2 loci are the less likely that recombination will occur between them

Block Two Cell Bio (9 decks)

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