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Biology > TH- Mitosis and cell cycles > Flashcards

TH- Mitosis and cell cycles Flashcards

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1
Q

What are the 3 functions of cell division?

A
  • Reproduction
  • growth
  • repair
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2
Q

what is a genome?

A

A cells genetic info packed as DNA

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3
Q

what is a somatic cell?

A

any diploid biological cell forming the body of an organism; that is, in a multicellular organism, any cell other than a gamete.

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4
Q

what is a gamete?

A

organism’s reproductive cells, haploid cells.

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5
Q

What is chromatin?

A

DNA + associated protein

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6
Q

what are genes?

A

units that specify an organism’s inherited traits

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7
Q

what form is a chromatin in when cell is not dividing?

A

long, thin chromatin fiber

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8
Q

what happens to chromatin before cell division?

A

During prophase, chromatin condenses into chromosomes

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9
Q

Describe the structure of a chromosome

A
  • 2 sister chromatids connected by a centromere

- each chromatid contains identical copies of DNA

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10
Q

what is mitosis?

A

formation of 2 identical daughter nuclei from the parent nucleus

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11
Q

what is cytokinesis?

A

division of the cytoplasm to form two seperate daughter cells

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12
Q

what are the 2 cell cycle phases?

A
  • interphase

- mitotic phase

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13
Q

which 5 phases make up mitosis?

A
  • Prophase
  • Prometaphase
  • Metaphase
  • Anaphase
  • Telophase(cytokinesis)
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14
Q

which 3 phases make up interphase?

A
  • G1
  • S phase
  • G2
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15
Q

what happens in each phase of interphase?

A
  • G1= growth phase, because this is the time in which a cell grows. cell synthesizes various enzymes and nutrients that are needed later on
  • S= cell synthesizes a complete copy of the DNA in its nucleus. It also duplicates a microtubule-organizing structure called the centrosome.
  • G2= The cell reproduces its organelles and makes sure everything is ready for the split.
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16
Q

Describe the 5 phases of mitosis

A

-prophase= The chromatin is condensing.
The nucleolus is beginning to disappear
the mitotic spindle is starting to form.
The centrosomes move away from each other, apparently propelled by lengthening microtubules.

-prometaphase= We now see discrete chromosomes; each consists of two identical sister chromatids
nuclear envelope fragments, and microtubules from the spindle interact with the condensed chromosomes.
Kinetochore microtubules from each pole attach to one of two kinetochores.
Nonkinetochore microtubules interact with those from opposite ends of the spindle.
spindle fibers push the sister chromatids towards the metaphase plate

-metaphase= The spindle is complete,asters have grown and the chromosomes, attached to microtubules at their kinetochores, are all at the metaphase plate.

-anaphase= Anaphase commences when the proteins holding the sister chromatids together are inactivated.
centromeres divide, separating the sister chromatids.
Each is now pulled toward the pole to which it is attached by spindle fibers.
does that ^ by ‘walking back’ as kinetochore is essentially a motor protein
The microtubules shorten by depolymerizing at their kinetochore ends

-Telophase= . Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divide the cytoplasm in two or cleavage furrow for animal cells.

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17
Q

How does the mitotic spindle elongate?

A

by incorporating more subunits of the protein tubulin.

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18
Q

what is an aster?

A

radial array of short microtubules, extends from each centrosome

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19
Q

How do the kinetochore microtubules go back towards their pole?

A

motor proteins on the kinetochore “walk” the attached chromosome along the microtubule toward the nearest pole.
Meanwhile, the excess microtubule sections depolymerize at their kinetochore ends.

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20
Q

What is the function of the nonkinetochore microtubules?

A

responsible for lengthening the cell along the axis defined by the poles.

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21
Q

describe the process of cytokinesis in animal cells

A
  • occurs by a process called cleavage.
  • first sign of cleavage is the appearance of a cleavage furrow in the cell surface near the old metaphase plate.
  • On the cytoplasmic side of the cleavage furrow is a contractile ring of actin microfilaments associated with molecules of the motor protein myosin which causes the ring to contract
  • the contraction deepens the furrow until the parent cell is pinched into 2 daughter cells
22
Q

describe the process of cytokinesis in plant cells

A
  • vesicles from the Golgi coalesce at the metaphase plate, forming a cell plate.
  • The plate enlarges until its membranes fuse with the plasma membrane at the perimeter.
  • The contents of the vesicles form new cell wall material between the daughter cells.
23
Q

how do prokaryotes reproduce?

A

binary fission

24
Q

describe the process of binary fission

A

1- chromosome replication begins at one point in the circular chromosome, the origin of replication site, producing two origins.
2-Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell
3-As the chromosome continues to replicate, one origin moves toward each end of the cell.
4-While the chromosome is replicating, the cell elongates.
5-Replication finishes. The plasma membrane grows inward, and new cell wall is deposited.
6-Two daughter cells result.

25
Q

why do scientists believe that ‘As eukaryotes evolved, the ancestral process of binary fission gave rise to mitosis’

A
  • Certain protists exhibit types of cell division that seem intermediate between binary fission and mitosis
  • Since prokaryotes evolved before eukaryotes, mitosis probably evolved from binary fission
26
Q

What evidence is there for the hypothesis ‘cell cycle appears to be driven by specific chemical signals’ in terms of G1 and S phase.

A

Fusion of an S phase cell and a G1 phase cell induces the G1 nucleus to start S phase.
This suggests that chemicals present in the S phase nucleus stimulated the fused cell.

27
Q

what are the sequential events of the cell cycle are directed by?

A

cell cycle control system.

28
Q

what is a checkpoint in a cell cycle?

A

critical control point where stop and go-ahead signals regulate the cycle.

29
Q

how are the signals transmitted within the cell?

A

by signal transduction pathways.

30
Q

where are the 3 major checkpoints?

A

G1, G2, M

31
Q

why is the G1 checkpoint considered the most important in most cells?

A
  • If the cell receives a go-ahead signal at the G1 checkpoint, it usually completes the cell cycle and divides.
  • If it does not receive a go-ahead signal, the cell exits the cycle and switches to a nondividing state, the G0 phase.
32
Q

Define growth factors

A

is a naturally occurring substance capable of stimulating cell proliferation, wound healing, and occasionally cellular differentiation.

33
Q

which 2 proteins are involved in the cell cycle control?

A

cyclins and cyclin-dependent kinases (Cdks)

34
Q

what do kinases do to other proteins?

A

activate or deactivate other proteins by phosphorylating them.

35
Q

what is MPF?

A
  • one cyclin-Cdk complex

- M-phase-promoting-factor

36
Q

Peaks in the activity of one cyclin-Cdk complex, MPF, correspond to peaks in …

A

[cyclin]

37
Q

what does MPF trigger/cause?

A

triggers the cell’s passage past the G2 checkpoint to the M phase.

38
Q

What are the 3 changes MPF causes?

A
  • MPF promotes mitosis by phosphorylating a variety of other protein kinases.
  • stimulates fragmentation of the nuclear envelope by phosphorylation of various proteins of the nuclear lamina.
  • triggers the breakdown of cyclin, dropping cyclin and MPF levels during mitosis and inactivating MPF.
39
Q

What does the M checkpoint ensure?

A

all the chromosomes are properly attached to the spindle at the metaphase plate before anaphase.

40
Q

what happens at kinetochores that have not yet attached to spindle microtubules?

A
  • signal to delay anaphase originates at kinetochores
  • This keeps the anaphase-promoting complex (APC) in an inactive state.
  • When all kinetochores are attached, the APC activates, triggering breakdown of cyclin and inactivation of proteins holding sister chromatids together.
41
Q

What stimulates the division of human fibroblast cells in culture?

A

platelet-derived growth factor (PDGF)

42
Q

what does PDGF do at a site of injury?

A
  • living organism, platelets release PDGF in the vicinity of an injury.
  • PDGF bind to tyrosine-kinase receptors of fibroblasts, a type of connective tissue cell.
  • This triggers a signal-transduction pathway that allows cells to pass the G1 checkpoint and divide.
  • this causes an increase in fibroblaststhat help heal the wound
43
Q

Describe density-dependant inhibition

A
  • Cultured cells normally divide until they form a single layer on the inner surface of the culture container.
  • If a gap is created, the cells will grow to fill the gap.
  • At high densities, the amount of growth factors and nutrients is insufficient to allow continued cell growth.
44
Q

Describe anchorage dependence

A
  • To divide, they must be anchored to a substratum, typically the extracellular matrix of a tissue.
  • Control appears to be mediated by pathways involving plasma membrane proteins and elements of the cytoskeleton linked to them.
45
Q

when does the abnormal behaviour of a cancer cell begin?

A

-when a single cell in a tissue undergoes a TRANSFORMATION that converts it from a normal cell to a cancer cell.

46
Q

What happens if the immune system doesnt destroy transformed cell?

A

cells that evade destruction proliferate to form a tumor, a mass of abnormal cells.

47
Q

what is a benign tumor?

A

abnormal cells that remain at the originating site and dont cause serious problems

48
Q

what is malignant tumor?

A

cells become invasive enough to impair the functions of one or more organs.

49
Q

What is metastisis

A

cancer cells often lose attachment to nearby cells, are carried by the blood and lymph system around the body to other tissues, and start more tumors

50
Q

What are the treatments for metastasizing cancers?

A

high-energy radiation and chemotherapy with toxic drugs.

51
Q

How do these cancer treatments work?

A
  • These treatments target actively dividing cells.
  • Chemotherapeutic drugs interfere with specific steps in the cell cycle.
  • For example, Taxol prevents mitotic depolymerization, preventing cells from proceeding past metaphase.
52
Q

Why do we experience side effects from chemotherapy?

A

due to the drug’s effects on normal cells.

Biology (15 decks)

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