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BIOL 1101 > Lecture 7: Cell Cycles > Flashcards

Lecture 7: Cell Cycles Flashcards

1
Q

How did you get to where you are

A

1) growth
2) divison

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2
Q

DNA in prokaryotes

A
  • DNA as hereditary information
  • Vast majority have singular circular DNA (bacterial chromosome)
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3
Q

the rate at which prokaryotic cells divide

A

maximum rate where DNA replication occupies most of period between cytoplasmic divisions

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4
Q

when replication is complete

A

cytoplasm divides

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5
Q

the bacterial cell cycle (3 periods)

A

1) growth of cells and initiation of DNA replication at origin of replication site (ORI)
2) DNA replication
3) Cell divides by binary fission

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6
Q

What is the origin of replication site

A

ORI (nucleotide site where replication originally starts)
- in the middle of the cell where enzymes for DNA replication are located
- Ori is at the middle because the enzymes are at the middle

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7
Q

Binary fission

A

division of cytoplasm to divide cells and chromosomes, where each cell gets 1 chromosome (for prokaryotes)

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8
Q

Step 1 of bacterial replication

A

INITIATION OF REPLICATION
- replication of bacterial chromosome begins at ORI

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9
Q

Step 2 of bacterial replication

A

DNA REPLICATION
- once the original duplicates, 2 ori’s will migrate towards the two ends of the cell as the rest of the chromosome is replicated
- active movement distributes two replicated chromosomes to two ends of cell (on opposite ends)

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10
Q

Cell Cycle

A

a period of growth followed by nuclear division and cytokinesis

  • eukaryotes: mitosis and meiosis
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10
Q

Eukaryotic Cell Cycle

A
  • multicellular eukaryotic organisms require strict control of cell division (out of ctrl growth can lead to tumors/cancer)
  • ultimately results in a mature body composed of different subpopulations of cells (i.e. WBC, rbc, skin cells that are formed through mitosis are the same genetically but are specialized, so they have different functions)
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11
Q

Step 3 of Bacterial replication

A

CYTOPLASMIC DIVISION
- inward growth of plasma membrane leads to pinching to eventually produce 2 daughter cells
- new cell wall material assembled
- cut cell into 2 parts (binary fission)

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12
Q

Cell Division

A

Mitosis: divides replicated DNA equally and precisely
- genetically similar to original cell (CLONE)

Meiosis: daughter cells with 1/2 the number of chromosomes
- genetically different from original cell

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13
Q

Clone

A
  • genetically similar to original cell
    essentially produces through mitosis, but the specialization makes the cells different but they are genetic clones
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13
Q

Difference between mitosis and meiosis

A

1) MITOSIS
- 2 new daughter cells
- clones

2) MEIOSIS
- 4 daughter cells
- 1/2 the number of chromosomes from parents: good because it makes them different genetically allowing for variation

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14
Q

DNA of eukaryotic cells

A
  • divided among individual, linear chromosomes
  • located in cell nucleus
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15
Q

what are chromosomes

A

nuclear units of genetic information that are divided and distributed

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16
Q

what is Ploidy

A

number of chromosome sets (cell or species)
- diploid (2n)
- haploid (n)

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17
Q

Diploid

A

humans: in majority of cells we will have 2 sets of chromosomes (46 chromosomes)

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18
Q

Haploid

A

specific algae, specific protists, prokaryotes will have haploids

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19
Q

Sister chromatids

A
  • Replication of DNA of each individual chromosome forms sister chromatids (2 identical molecules)
  • Attached pair of duplicated chromosomes, at this point they’re only considered 1 chromosomes (they’re formed before forming new cells, its just the product of multiplying chromosomes)
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20
Q

Polyploidy

A

multiple chromosome sets
- triploid and tetraploid are also possible, plant species

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21
Q

Non homologous

A

Chromosome with different genes
- chromosome 4 and 19 for example are non-homologs

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22
Q

Homologs chromosomes

A

chromosomes have same genes arranged in same order
Ex. the pair within a set

For ex: We have diploids: such as 2 chromosome 11’s those are homologs, they are the same gene arranged in the same order

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23
Q

sister chromatids are 2 ____ molecules

A

2 identical molecules

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24
Q

Sister chromatids eventually become

A

independent daughter cells

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24
Q

Mitotic cell cycle

A

-2 major phases: interphase (period of growth) and mitosis (period of division)

MITOSIS HAS 5 PHASES
1) prophase
2) prometaphase
3) metaphase
4) anaphase
5) telophase

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24
Q

Chromosome segregation

A

Separation of sister chromatids and equal distribution to each of 2 cells resulting from cell division

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25
Q

G1

A

*period of growth before DNA replicates
- majority of growth occurs here
- spend most of their time here: amount of time depends on the

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26
Q

the time spent in G1 depends on

A
  • signals the cell gets
  • environment of the cell
  • type of cell
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27
Q

G0

A
  • cell cycle arrest
  • cell exit cycle:
  • no longer participate in cell cycle
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28
Q

what’s an example of a cell that would exit G0

A

nerve cells
- therefore, its difficult to replace nerve tissue because its hard to replace them since they exit therefore neurodegenerative diseases are hard to treat

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29
Q

Interphase

A

G1,G2,S (majority of cycle)

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30
Q

G2

A
  • period after DNA replicates
    cell prepares for division

SHORT

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31
Q

Mitosis

A
  • cytoplasm divides independent of mitosis beginning but occurs at end of mitosis
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32
Q

where does interphase end

A

parent cell

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33
Q

Timing for cell cycle

A

G1: Variable Time
S: 10-12 H
G2: 4-6 H
Mitosis: 1-4 H

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34
Q

Phase 1: Interphase
- G1 PHASE

A

New cells goes straight here
- Daughter cell from previous
division cycle enters initial period of cytoplasmic growth (building new macromolecules, organelles, etc)
- No DNA replication

GOES TO S commitment

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35
Q

Phase 1: Interphase
- S PHASE

A
  • DNA replication (building new DNA, each chromosome replicates)
  • Chromosomes duplicate (stay together at sister chromatids)
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36
Q

Phase 1: Interphase
- G2 PHASE

A
  • synthesize RNA and protein
  • NO DNA replication
  • Get ready for cell division

building more RNA and DNA to prep for cell

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37
Q

chromosomes in interphase

A
  • during all steps of interphase, chromosomes are relatively loose but organized in nucleus

(loose arrangement)
- DNA wraps itself loosely, because that way enzymes get to DNA in transcription and translation

38
Q

what happens in S phase (hint: cytoskeleton)

A

W/ Duplication of chromosomes, centrosomes will also duplicate

  • major component of cytoskeleton
  • main microtubule organizing center
39
Q

Mitosis Stage 1: Prophase

A
  • Chromosomes condense into compact rod-like structures
    *prevents enzymes from coming on from transcription and replication
  • Sister chromatids held together by a centromere
    region that is in the middle of sister chromatids, holds them together
  • Spindle forms in the cytoplasm between 2 centrosomes
    To build microtubules that make up spindle which moves chromosomes around
40
Q

why do we want to prevent enzymes for transcription and replication

A

we are in mitosis, we don’t want this to happen yet, by compacting our chromosomes we can accurately divide so each cell gets the right number of chromosomes

41
Q

What happens to nuclear envelope around chromosomes

A

break down

42
Q

DNA wrapping

A
  • DNA complexed with histone proteins to fit into nucleus
  • 2 each of H2A, H2B, H3. H4 histones= 8 protein nucleosome core particle attach to DNA molecule, combined tight loop=nucleosome
  • mutliple nucleosomes are coiled and stacked forming chromatin
43
Q

Histone H1 causes what

A

nucleosomes to package into a coiled structure (solenoid)

  • btw H1 is the 5th type of histone
44
Q

charge of Nucleosomes and Chromatin Fiber

A

DNA = sugar and phosphate backbone that have a -q
therefore, the +q of histones attracted to -q of DNA

45
Q

how exactly do we compact chromosomes

A

wrapping our DNA makes it compact which sets our chromosomes to be compact

46
Q

Mitosis Stage 2: Prometaphase

A
  • Nuclear Envelope breaks down and disappears which allows for:
  • Spindle entering former nuclear area because
  • Microtubules from opposite spindle poles attach to 2 kinetochores of each chromosome (does not attach to DNA)

*kinetochores are on the outside of centromere/chromosome

47
Q

Kientochores

A

protein complex that attaches chromosomes to spindle fibers during cell division.

Kinetochore attach the sister chromatids at centromere (complex of different proteins)

48
Q

Mitosis Stage 3: Metaphase

A
  • Spindle is fully formed
  • Chromosomes align at spindle midpoint, moved by spindle microtubules
    this is where we do genetic analysis chromosomes are most intense
49
Q

Karyotype

A

Importance of karyotypes:

1) determines number of chromosomes in cell

2) size of chromosomes: dependent on number of genes and DNA on chrosomes
- Allows us to determine problems

3) Determines sex of human

50
Q

When is karyotype checked

A

Metaphase: bc chromosomes are most condensed and visible, making it easier to observe their structure and number

51
Q

Mitosis Stage 4: Anaphase

A
  • spindle spectates sister chromatids and moves them to opposite spindle poles
  • Chromosome segregation is complete

***(kinetochores are directly involved: help align and separate chromosomes during cell division, ensuring accurate chromosome distribution to daughter cells.)

52
Q

Mitosis Stage 5: Telophase

A

Chromosome decondense
- Return to extended state typical of interphase (loose phase)

Spindle Disassembles

  • New nuclear envelope forms around chromosomes
  • We start division of cytoplasm now
  • End of nuclear division yielding 2 nuclei
53
Q

Cytokinesis

A

Division of cytoplasm completes cell division

Produces 2 daughter cells:
- each daughter nucleus produces by mitosis
- genetically identical to parental cell

54
Q

Cytokinesis in Animal Cells

A

Furrowing : microfilaments are tightened until plasma membrane can be pinched off

Band of microfilaments forms just inside the plasma membrane, forming belt

microfilaments slide together and tighten (become so tight)
- form furrow in plasma membrane

  • separates cytoplasm in 2 parts
55
Q

Cytokinesis in Plants

A
  • vesicles will come from Golgi with cellulose that will fuse to make a new cell wall and divide cell into 2 *
  • Cell wall material in deposited along plane of former spindle midpoint
  • Deposition continues until continuous new wall (cell plate) separates daughter cells
  • stretches across former spindle midpoint
56
Q

Spindle Formation

A

1) In Animal Cells
CENTROSOME:
- main microtubule organizing centre (MTOC)
- contain a pair of centrioles
- divides and move apart

Microtubules form early spindle

2) In Plant Cells
NO CENTROSOME:
- spindle forms from multiple MTOCs (still make microtubules and have organizing centres)
- Assemble in all directions surrounding nucleus

57
Q

what happens in the spindle

A

kinetochore microtubules will connect chromosomes to spindle pores (binds to sister chromatid)

Nonkinetochore microtubule
- Extend between spindle pores without connecting to chromosomes

  • At spindle midpoint, microtubules from 1 pole overlap with those from opposite
58
Q

As the length of the nonkinetochore microtubules increase

A

It will stretch the cell which increases the distance between sister chromatids for cytokinesis to happen away from the equator
* don’t touch sister chromatids

59
Q

How do chromosomes move

A

Chromosomes move through the shortening of microtubules, aided by motor proteins and enzymes like kinesin and dynein, which help pull them toward opposite poles.

microtubules remain stationary
tubulin- protein that forms microtubules

60
Q

How do we know microtubules remain stationary

A

We know microtubules remain stationary because fluorescence-marking experiments reveal that they stay in place while motor proteins move along their length.

  • no movement of a bleached site
61
Q

Cell Cycle CTRL

A
  • complexes of cyclin and a cyclin decedent protein kinase (CDK)

Cyclin: A protein that regulates the cell cycle by activating cyclin-dependent protein kinases.

Cyclin-dependent protein kinase (CDK): An enzyme that, when activated by a cyclin, phosphorylates target proteins to drive cell cycle progression.

62
Q

CDKs

A

Activated when combined with a cyclin
- adds PO4 groups to target proteins

63
Q

Different cyclin and CDK combinations

A

regulate cell cycle transitions at different checkpoints

  • cyclin level fluctuates during cell cycle
  • CDK activity levels also fluctuate during cell cycle

IMPACT OF FLUCTUATION:
regulate the cell cycle progression by activating specific target proteins through phosphorylation, with cyclin levels rising and falling at precise stages to ensure proper timing and transition between phases.

64
Q

FULL CYCLIN/CDK CTRL
(internal mechanisms)

A

1) DURING G1
- cyclin E levels RISE
- CDK2 activity RISES
= cell passes G1-S checkpoint

2) S CYCLIN BINDS TO CDK2
- cyclin A RISE
- CDK2 activity RISES
= cell completes S Phase

3) ACTIVTED CDK1
- cyclin B levels RISE
- CDK1 activity RISES
= cell passes the G2-M checkpoint

  • cyclin is degraded
64
Q

If a cell passes from G1 to S

A

it must finish cycle

65
Q

enzymes that phosphorylate proteins

A
  • only if they’re bound on a cyclin, put through as a combo
66
Q

we must regulate the cycle because

A

it will prevent abnormal cell growth

66
Q

How do we see Contact Inhibition

A

PETRI DISH
- cells will grow and divide until dish is filled and then contact inhibition

CANCER CELLS
- lost ability of contact inhibition to grow on top of each other which forms tumours

67
Q

external mechanisms

A

Based on surface receptors that recognize and bind signals: (can tell cells to speed up, slow down, turn on/off)
- peptide hormones and growth factors
- cell-surface molecules
- molecules of the ECM

  • Binding triggers internal reactions that speed, slow, or stop cell divison
  • Contact Inhibition- contact triggers a stop cell division response
68
Q

Contact Inhibition

A

contact triggers a stop cell division response
- receptors of one cell touch another when too close a cell is signal and the rate of cycle will slow down

69
Q

Asymmetrical Cell Division

A
  • Stem cells in animals and plants exhibit asymmetrical cell division
  • asymmetrical: differ from how many regulatory proteins they have which controls transcription, translation, and gene expression *
  • Creates two different pools of daughter cells
    1) Progenitor Cell (divides definitely, undergoes specialization)
    2) Stem Cell (divides infinite times)
70
Q

proteins will make a cell become a progenitor cell

A

in time will become specialized on the path

71
Q

asymmetrical divison

A

the proteins they get determines what they are/become

72
Q

Cells cant divide indefinitely

A

triggers cellular senescence (cell aging)
- loss of proliferative ability over time

1) DNA damage
- Mutations: issue with duplicating DNA, A threshold of mutations will tell cells to stop growing and dividing so that they mutation doesn’t pass on

2) Telomere shortening
- extensions on end of chromosomes made of nucleotides
Have 0 genes but they protect our genes on our chromosomes so as cells keep dividing, the telomeres keep shortening
- we cant risks the loss of protection, triggering cells to stop and triggers cell aging

73
Q

Cancer

A

CTRL of cell division is lost (to respond to internal/external factors to stop cell growth and division)

  • cell divide continuously and uncontrollably
  • form rapidly growing mass of cells that interfere with body functions
  • ONCOGENES: mutated genes that cause cancer
  • normally, these are normal genes but they become mutated to cause cancer

Cancer cells break loose from their original tumours in a process called metastasis
- form additional tumours in other parts of the body

74
Q

Tumours take residence somewhere else in the body

A

Secondary Tumours
- tumours have a greater density of cells

75
Q

Apoptosis

A

programmed cell death
- very ancient mechanism that’s common to all multicellular eukaryotes studied
- initiation of cell death results from internal+external signals
- involves activation of caspases-protease enzyme

76
Q

Caspases

A
  • triggered by signal transduction and occur in all eukaryotes *
  • enzymes that belong to proteases and break down protein in cells
  • protein carry out cellular function therefore, enzymes would stop function

BC
- there are times when cells you needed at development are no longer useful
- damaged cells
- cells behaves improperly (precancerous cells)
TRIGGER APOPTOSIS

77
Q

Nematode Caenorhabditis elegans

A

Early experiments to model apoptosis
- because its translucent so body could be seen

An Adept Signal
- on surface of mitochondria, adept signals with activation of specific genes
* NUCLEASES will be activates and break down DNA and distrust mitochondria to prevent ATP synthesis)

78
Q

what do microtubules make up

A

spindle, move chromosomes around

79
Q

when nutrients are abundant in prokaryotic cells, what can be observed

A

not as much of a need for a B period (G1) since they can grow quickly enough to divide their cytoplasm as soon as DNA replication is complete + chromosomes are separate

80
Q

when the nucleus divides

A

the chromosomes are segregated

81
Q

THE 3 STAGES OF MITOSIS AND THE EUK CELL CYCLE

A

1) elaborate master program of molecular checks and balances to ensure proper progression

2) process of DNA synthesis replicates each chromosomes into 2 perfect copies

3) Structural and mechanical web of interwoven cables and motors of cytoskeleton to separate the replicated DNA into daughter cells

82
Q

how are newly formed sister chromatids held

A

via cohesins

  • cohesins are removed during mitosis and sister chromatids are thus seperated
  • the removal is precise leading to proper distribution of chromosomes=chromosomal segregation
83
Q

clones are exactly identical t/f

A

F- genetically very similar but not strictly identical

84
Q

cells can remain in interphase forever t/f

A

T

85
Q

what is a linker

A

short segment of DNA that extends between nucleosomes

86
Q

RNA synthesis in mitosis

A

as DNA is condensed, the nucleolus becomes smaller and eventually disappears, reflecting a shutdown of RNA synthesis

  • when chromosomes are decondensation the nucleolus, reappears and RNA transcription resumes (at this point, the cytoskeleton returns to interphase and nuclear division is complete with 2 nuclei)
87
Q

when Is chromosomal segregation complete

A

when daughter chromosomes have reached the 2 poles

88
Q

mitotic spindle

A
  • in cytoplasm, mitotic spindle begins to form between two centrosomes as they migrate towards opposite ends to form spindle poles
89
Q

mathematical relationship between chromosomes and amount of DNA

A
  • before: 1 chromosome is 1 DNA double helix
  • after: 1 chromosomes is 2 DNA double helixes
  • DNA replication increases the amount of DNA in the nucleus but NOT THE NUMBER OF CHROMOSOMES

thus, each of the 2 daughter cells receives 1 of the 2 sister chromatids from each replicated chromosome

90
Q

asters

A

centrosomes at the spindle tips which form the poles of the spindle

type of centrosome that makes spindle pores

91
Q

how are microtubules formed in plants

A

microtubules that assemble in all directions from multiple MTOCs to surround the entire nucleus

92
Q

what happens to tubulin as the kinetochores pass along the microtubules

A

the tubulin will disassemble
- microtubules will become shorter

93
Q

Cell Cycle Arrest Scenarios

A

G1/S CHECKPOINT
- DNA is damaged by radiation or chemicals
- G1/S is where we read extracellular signals so if we don’t have a necessary signal/hormone=arrest

G2/M CHECKPOINT
- DNA not fully replicated in S
- DNA damage
- we need complete DNA replication

MITOTIC CHECKPOINT
- whether chromosomes are attached properly to mitotic spindle so that they’ll align correctly
- essential for proper number of daughter cells

94
Q

local area where stem cells divide

A

niche

95
Q
A

BIOL 1101 (16 decks)

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