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The Cell Cycle Flashcards

1
Q

What best distinguishes living vs non-living?

A

The ability to reproduce

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2
Q

Key Function of Cell Division (3):

A

1) Asexual Reproduction

2) Growth and Development

3) Cell Replacement

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3
Q

Asexual Reproduction

A

Unicellular organisms divide to form individual organisms

–> Prokaryotes, unicellular eukaryotes (yeast, amoebas, etc.)

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4
Q

Cell Division’s Role in Growth and Development

A

Multicellular organisms divide to grow –> Enables organisms to develop from a single cell to a complex cell system

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5
Q

Cell Division’s Role in Cell Replacement

A

Tissue renewal/repair:

Replacing cells that die from accidents or normal wear and tear

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6
Q

What must be highly coordinated for proper cell division?

A

The timing of DNA replication and the actual cell division

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7
Q

Genome

A

All of a cell’s DNA (all the genetic info)

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8
Q

Eukaryote vs Prokaryote Genome

A

Eukaryotes = Genome containing multiple DNA molecules

Prokaryotes = Genome containing usually only one DNA molecule

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9
Q

Chromosomes

A

DNA wrapped in protein –> DNA-Protein Complex

–> Carry genes which specify an organism’s inherited traits

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10
Q

Gene

A

A segment of DNA

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11
Q

Replicated vs UN-replicated chromosomes

A

Replicated Chromosome = “X Shape” –> TWO DNA molecules

UN-Replicated Chromosome = NOT “X shape”
–> ONE DNA molecule

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12
Q

When in the cell cycle do we see replicated chromosomes?

A

During cell division (mainly mitosis)

–> DNA is usually kept in its unreplicated form

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13
Q

What do the chromosome proteins do?

A

Control chromosome structure (folding) and function (gene expression)

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14
Q

Chromatin

A

All the DNA and proteins of chromosomes

–> (kind of referring to all chromosomes)

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15
Q

Every species has a ________________ ______________ of chromosomes

A

1) Characteristic
2) Number

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16
Q

of chromosomes DOES NOT EQUAL

A

sophistication

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17
Q

Human Somatic Cells Chromosomes

A

46 Total Chromosomes –> 23 pairs (one from mom and the other from dad to form the pairs)

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18
Q

Gamete Chromosomes

A

1/2 the number of chromosomes as a somatic cell

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19
Q

Form of DNA when NOT dividing

OR

when DNA is REPLICATING!

A

Each chromosome is in the form of a long, thin chromatin fiber (uncondensed/uncoiled)

–> Cannot see using light microscope

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20
Q

Form of DNA AFTER Replication

OR

When cell is dividing

A

The chromosomes condense; each chromatin fiber becomes densely coiled and folded (“X shape”)

–> CAN see using a light microscope

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21
Q

Sister Chromatids

A

Copies of the same chromosome that are joined together (make up the classing “X shape’)

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22
Q

What holds sister chromatids together?

A

Cohesins

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23
Q

Cohesins

A

Proteins that hold sister chromatids together along their length

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24
Q

Centromere

A

A specialized sequence of DNA where sister chromatids most CLOSELY attach/tether

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25
A centromere is NOT a _______________ A centromere IS a _________ _______________
1) Location 2) DNA sequence
26
How do centromeres cause greater tethering between the sister chromatids?
Due to proteins that recognize and bind to centromere DNA
27
Importance of centromere
Important for proper splitting of the sister chromatids during segregation
28
Chromosome Arm
The portion of a chromosome to either side of the centromere
29
Cell Cycle
The life of a cell from the time it is first formed during division of a parent cell until its own division into 2 daughter cells
30
Two main processes must alternate to allow for proper cell division:
1) Doubling the genome --> Chromosome replication 2) Separation of the duplicated genome into exactly one half --> Chromosome segregation
31
The cell cycle is split into two overall phases
1) Interphase 2) M-Phase
32
Steps of Interphase
1) G1 phase 2) S phase 3) G2 phase
33
Purpose of Interphase
Sets up and readies the cell to undergo mitosis and cell division --> Accounts for around 90% of the cell cycle
34
M-Phase
1) Mitosis 2) Cytokinesis
35
G1 Phase
"First Gap" AKA First Growth --> Cell grows, producing proteins and cytoplasmic organelles
36
S Phase
"Synthesis" phase --> DNA/chromosome replication: the cell duplicates its chromosomes
37
G2 Phase
"Second Gap" AKA Second Growth --> Cell continues to grow AND completes preparations for the cell to divide --> **** The centrosome duplicates****
38
MTOC
Microtubule Organizing Centers --> Structure from which microtubules emerge
39
What is the Microtubule Organizing Centers (MTOC) in animals?
Centrosome
40
Centrosome
A microtubule organizing center for the formation of the mitotic spindle --> Made of TWO centrioles that are at a 90 degree angle to each other
41
How many centrosomes are needed in cell division?
Two
42
When does the centrosome duplicate?
In Interphase: G2 Phase
43
Mitosis
Nuclear division (separation of replicated chromosomes)
44
Steps to Mitosis:
1) Prophase 2) Pro-metaphase 3) Metaphase 4) Anaphase 5) Telophase (PpMAT)
45
Prophase (3)
3 main events take place: 1) Centrosomes begin separating die to the lengthening of the microtubules between them (formation of an early mitotic spindle) 2) Chromosomes condense (into their classic "X shape") 3) Nucleoli disappear
46
Is the nuclear envelope still present in prophase?
Yes
47
What causes mass cell reorganization in prophase?
The depolymerization of cytoskeletal microtubules to release tubulin that is then recruited for formation of the mitotic spindle
48
Pro-Metaphase (3)
3 main events take place: 1) Nuclear envelope fragments 2) Kinetochores form at each centromere of the chromosomes (2 per chromosome: 1 on each sister chromatid) 3) Microtubules from the spindle begin attaching to the kinetochores (progressing towards alignment in the middle)
49
Kinetochores
A protein complex that assembles on the centromere of each sister chromatid
50
How do kinetochores bond to the centromere?
Some proteins of the kinetochore are DNA binding proteins that recognize the centromere DNA sequence, making the kinetochores from there
51
Kinetochore Analogy
Kinetochores are like "landing pads" for microtubules
52
Metaphase (3)
3 main events take place: 1) Centrosomes are now at EXACTLY opposite poles 2) Chromosomes have all arrived at the metaphase plate (middle) 3) All kinetochores are attached to kinetochore microtubules
53
Metaphase Plate
An imaginary plane exactly midway between the poles of the cell
54
What causes the chromosomes to align at the metaphase plate?
A tug of war --> Microtubules are pulling and pushing which puts OPPOSING FORCES on the chromosomes attached
55
What conditions of the "tug of war" must be met in order for the chromosomes to align in the middle?
The opposing forces placed on the chromosomes by the microtubules must be EQUAL --> The chromosomes align in the middle and metaphase is "reached"
56
Anaphase (2)
2 main events take place: 1) Sister chromatids separate suddenly and get pulled to opposite sides of the cell 2) Non-Kinetochore microtubules elongate which causes the cell to also elongate overall --> The SHORTEST step of mitosis
57
What begins anaphase?
The Anaphase Promoting Complex (APC)
58
Anaphase Promoting Complex (APC)
A protein complex that has PROTEASE activity that, when activated, cleaves (cuts) COHESINS
59
What activates APC?
TENSION --> Kinetochore-microtubule interactions must be oriented specifically to achieve a level of tension that in turn ACTIVATES APC
60
What is the correct kinetochore interaction with microtubules?
Microtubules from each respective side connect to the kinetochore closest to the side of their origin (BOTH kinetochores must be bonded to a microtubule) --> "Back to back" attachment --> Produces the sufficient tension that activates APC
61
How does the APC protect the cell?
Anaphase will be delayed until all chromosome kinetochores have been properly attached to the microtubules --> This ensures proper chromosomal segregation and that there are no errors when pulling the chromatids apart ***Protects against improper segregation of the DNA***
62
What does APC do once activated?
APC proteases CLEAVE the cohesins holding the sister chromatids together which then allows the microtubules to pull them apart and to opposite poles
63
Telophase (4)
4 main events take place: 1) 2 daughter nuclei begin to form (along with their nuclear envelopes) 2) Nucleoli Reappear 3) Chromatin becomes less tightly coiled --> **Cannot be seen under light microscope at this point 4) Removal of the mitotic spindle: Any remaining spindle microtubules DEPOLYMERIZE --> MITOSIS IS COMPLETE AT THIS POINT
64
Cytokinesis
Cytoplasmic Division --> Leading to (usually) 2 daughter cells (Process is slightly different between animals and plants)
65
When does cytokinesis begin?
Generally begins during ANAPHASE or TELOPHASE
66
What marks the beginning of cytokinesis?
Formation of the cleavage furrow (in animals)
67
Around when does the cleavage furrow begin to form?
Around LATE ANAPHASE
68
Cleavage Furrow
A shallow groove in the cell surface near the old metaphase plate --> A CONTRACTILE RING OF ACTIN MICROFILAMENTS
69
What causes the cleavage furrow to contract/pinch in?
The contractile ring of actin microfilaments associate with myosin protein molecules allowing the ring to contract
70
What happens as the cleavage furrow ring contracts?
The cleavage furrow deepens until the parent cell is pinched into 2 = 2 daughter cells
71
Cytokinesis Proces in PLANTS
1) During TELOPHASE, vesicles derived from the golgi apparatus move along microtubules to the middle of the cell 2) Vesicles COALESCE in the middle of the cell = CELL PLATE 3) Cell plate enlargens until the membrane surrounding the plate fuses with the membrane along the perimeter of the cell = 2 daughter cells with individual plasma membranes --> Cell wall then forms between the two cells
72
In plant cytokinesis, what do the vesicles carry?
Materials used for building the cell plate and wall
73
Binary Fission
= "Division in half" A type of asexual reproduction typically observed in prokaryotes and a select few unicellular eukaryotes
74
Binary Fission in Eukaryotes vs Prokaryotes
Eukaryotes = Involves mitosis Prokaryotes = NO mitosis
75
Bacterial Binary Fission
1) Chromosome replication begins at the origin = two copies of the origin, one of the copies moves to the other end of the cell 2) Origins are at 2 opposite ends of the cell --> Replication continues and cell continues to grow 3) Replication finishes and the cell is roughly double its original size = Plasma membrane pinches inwards (by a tubulin like protein) 4) New cell wall is deposited and cell division is complete
76
Bacterial chromosome is _________ and ________...
circular and attached to the cell membrane
77
In bacterial binary fission, all newly synthesized DNA is...
Attached to the plasma membrane
78
Mitotic Spindle
A microtubule based machine: Provides MECHANICAL FORCE that drives the alignment of chromosomes during Metaphase AND the separation of sister chromatids during anaphase
79
Origins of the mitotic spindle
centrosomes
80
What is the mitotic spindle made up of?
Consists of fibers made of microtubules and associated proteins
81
3 types of microtubules in the mitotic spindle:
1) Astral MT 2) Kinetochore MT 3) Overlap ("Non-kinetochore") MT
82
Astral Microtubules
A radial array of short microtubules that extend out from each centrosome (Gives the "star" appearance of the aster)
83
Kinetochore Microtubules
Microtubules that actually attach to chromosome kinetochores
84
Overlap Microtubules
AKA Non-Kinetochore MT --> Microtubules that DO NOT bind to kinetochores but elongate to overlap and interact with each other
85
Mitotic Spindle Through the Phases
Interphase === Centrosome duplicates Early Prophase === 2 centrosomes are adjacent on the nuclear membrane Prophase === Microtubules grow --> Centrosomes pushed apart Metaphase === Each mitotic spindle is at opposite ends of the cell Telophase === Mitotic spindle deforms

BIO 202 (33 decks)

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