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SG Molecular > Lecture 26: Meiosis And Fertilization > Flashcards

Lecture 26: Meiosis And Fertilization Flashcards

1
Q

What are the 5 phases of mitosis?

A 
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
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2
Q

What aspect of the cytoskeleton is essential for proper segregation of chromosomes?

A

Microtubules, including their motor proteins

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3
Q

What aspect of the cytoskeleton is required for the actual division of one cell into 2 daughter cells following mitosis?

A

Actin

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4
Q

What protein is important in mitosis and meiosis to compact the chromosomes so that they are not tangled and easier to separate?

A

Condensin

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5
Q

When does DNA replication take place?

A

S phase of interphase

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6
Q

What is the purpose of the centrosome cycle?

A

Duplication of centrosomes

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7
Q

What forms the two poles of the mitotic spindle?

A

Centrosomes

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8
Q

Duplication of the centrosomes takes place at the same time as what?

A

DNA replication (via G1/S-Cdk and S-Cdk)

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9
Q

If you are looking through a microscope at a cell and you notice:

  • a distinct nucleus
  • chromosomes that are not condensed
  • twice as much DNA

What phase of the cell cycle is occurring?

A

G2 of interphase

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10
Q

If you are looking through a microscope at a cell and you notice:

  • centrosomes
  • distinction of individual chromosomes
  • distinct nuclear envelope

What phase of the cell cycle is occurring?

A

Prophase

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11
Q

What protein holds the chromosomes together along their length?

A

Cohesin

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12
Q

When does mitotic spindle assembly first occur?

A

Prophase

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13
Q

Which type of microtubules are considered non-kinetochore microtubules?

A

Interpolar microtubules

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14
Q

What distinguishes kinetochore microtubules from interpolar microtubules?

A

They bind to the chromosomes themselves

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15
Q

What motor protein is most important in establishing the mitotic spindle, and which way does it move?

A

Kinesin - moves toward plus end

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16
Q

Dynein is directed toward the _________ end and it moves toward the _______ of the cell

A

Minus; center

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17
Q

During mitotic spindle assembly, what phosphorylates microtubule-associated proteins, thus contributing to dynamic instability?

A

M-Cdk

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18
Q

What stabilizes interpolar microtubules?

A

Crosslinking of motor proteins - Kinesins and Dynein

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19
Q

If you are looking through a microscope at a cell and you notice:

  • no more nuclear membrane
  • condensed chromosomes
  • chromosomes easily distinguished
  • mitotic spindle well established at poles of cell

What part of the cell cycle is occurring?

A

Prometaphase

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20
Q

What signals the sister kinetochores that they are attached correctly?

A

Tension generated by binding at each side, each microtubule needs to feel some resistance coming from the other side

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21
Q

When the chromosomes are pulled toward the poles, is this the plus or minus direction?

A

Minus

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22
Q

True or false: motor proteins and chromosomes cannot direct the assembly of a functional spindle in the absence of centrosomes

A

False, they can!

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23
Q

______ motors anchored in the cell membrane pull on astral microtubules

A

Dynein

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24
Q

If you are looking through a microscope at a cell and you notice:

  • everything lined up in the middle
  • elongated mitotic spindle

What phase of the cell cycle is occurring?

A

Metaphase

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25
Q

What dictates where the contractile ring will form for cell division?

A

Metaphase plate

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26
Q

True or false: in a multicellular area, the cells become synchronized so that they are dividing around the same time

A

True

27
Q

What is the primary event that must occur during anaphase and what triggers this event?

A

Cohesin must break down, triggered by APC/c

28
Q

If you are looking through a microscope at a cell and you notice:

  • cohesin has broken down
  • chromosomes are at the poles of the cells

What phase of the cell cycle is occurring?

A

Anaphase

29
Q

Anaphase requires Anaphase Promoting Complex (APC) which tags _________ with ubiquitin, leading to its degradation

Loss of this protein frees _________, an enzyme that helps break chromatids apart by digesting cohesin

A

Securin

Separate

30
Q

If you are looking through a microscope at a cell and you notice:

  • inward pinching d/t contractile ring
  • chromosomes are less distinct
  • beginnings of nuclear envelope

What phase of the cell cycle is occurring?

A

Telophase/cytokinesis

31
Q

What is the effect of Cdks in the breakdown of the nuclear membrane?

A

Cdks phosphorylate nuclear pore proteins and laminin, causing breakdown of the nuclear membrane

32
Q

What are the 2 cytoskeletal machines responsible for mechanical processes in M phase?

A 
Mitotic spindle
Contractile ring (actin)
33
Q

What is characteristic of the contractile ring seen in anaphase?

A

Cleavage furrow

34
Q

How does cytokinesis in plant cells differ from that of animal cells?

A

In plants, phragmoplast forms (remains of mitotic spindle - interpolar microtubules)

New cell wall forms from cellulose microfibrils, there is no pinching

35
Q

What are some competitive advantages in organisms that utilize sexual reproduction?

A

“Reshuffling” genetic info, speeds up deletion of deleterious mutations, genetic variation favored by natural selection

36
Q

What is the major driving force for genetic diversity/variation?

A

Mutation, closely followed by crossing over in meiosis

37
Q

Compare mitosis vs. meiosis in terms of what cell type is involved with each

A

Germline = meiosis

Somatic cells = mitosis

38
Q

Are gametes produced by the ovaries and testes at sexual maturity haploid or diploid?

A

Haploid

39
Q

How many pairs of chromosomes in human somatic cells?

A

23

40
Q

What does it mean to say that the two chromosomes in each of the 23 pairs in somatic cells are homologous?

A

They have the same genes in the same locations

41
Q

Each gene has a specific location called a ______ on a certain chromosome

A

Locus

42
Q

The 22 pairs of chromosomes that do not determine sex are called ___________

A

Autosomal

43
Q

How many sets of chromosomes does a diploid cell have?

A

2 sets (2n)

44
Q

What is the diploid number in humans?

A

46 (2n = 46)

45
Q

Meiosis results in a _________ germ cell. Fertilization generates a ________ zygote.

A

Haploid

Diploid

46
Q

For humans, the haploid number is _____

A

23 (n = 23)

47
Q

What is the key indicator that two chromosomes are homologues?

A

They are the same length

48
Q

What is the term describing homologues coming together for crossing over?

A

Synapsis

49
Q

Cohesin holds sister chromatids together. What is responsible for holding tetrad homologues together?

A

Cohesin!

50
Q

T/F Crossing over happens all along the entire length of the chromosomes

A

True

51
Q

When does crossing over occur?

A

Prophase I of Meiosis I

52
Q

What does haploid/diploid refer to?

A

The NUMBER of chromosomes. 2 sister chromatids = haploid because these still make up ONE chromosome

53
Q

What is the difference in cohesin breakdown during mitosis vs. meiosis?

A

Mitosis - cohesin breaks down between sister chromatids at anaphase

Meiosis I - cohesin breaks down along tetrads only

Meiosis II - cohesin breaks down between sister chromatids

54
Q

True/False: crossing over only occurs between sister chromatids

A

False! Crossing over only occurs between HOMOLOGUES

It would be pointless for sister chromatids to cross over because they are identical

55
Q

When does synapsis occur during mitosis?

A

IT DOESN’T

56
Q

3 EVENTS are unique to meiosis, and all of them occur during ___________

A

Meiosis I

57
Q

What are the 3 events that are unique to meiosis?

A
  • Synapsis and crossing over in prophase I
  • Paired tetrads align at metaphase plate (instead of individual chromosomes)
  • anaphase I involves separation of homologous chromosomes instead of sister chromatids
58
Q

What carries out the actual crossing over?

A

Synaptonemal complexes

59
Q

What is the term for areas where crossing over is currently occurring?

A

Chiasmata (chiasma)

60
Q

What do chromosome pairing and crossing-over ensure?

A

Proper segregation

61
Q

What are the 3 mechanisms to contribute to genetic variation outside of mutation?

A

Random fertilization, independent assortment of chromosomes, crossing over

62
Q

How does independent assortment contribute to genetic variability?

A

Tetrads can line up at the metaphase plate differently; different combos lead to different possibilities

63
Q

True or false: errors in meiosis may occur during crossing over and also during meiosis I or II

A

True

SG Molecular (7 decks)

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