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Fall 2023 > BIOL. 1406: Cell Cycle > Flashcards

BIOL. 1406: Cell Cycle Flashcards

1
Q

How does one parent cell give rise to two daughter cells?

A

1) Interphase: the cells grows in preparation for cell divisions; chromosomes are duplicated with genetic material copied precisely
2) Mitosis: the chromosomes are separated from each other to opposite ends of cell
3) Cytokinesis: the cell divides into two daughter cells genetically identical to each other and the parent cell

-the daughter cells may go on to divide, repeating the cycle

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2
Q

Cell Division

A

reproduction of cells; all continuity of life is based on it;
the ability of living organisms to produce more of their own kind is the one characteristic that distinguishes living organisms from non-living matter

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3
Q

Key Roles of Cell Division

A
  • single-celled organisms give rise to new organisms through cell division
  • multicellular organisms undergo embryonic development through cell division
  • fully grown multicellular organisms use cell division for renewal or repair of tissue
  • cell division is accurate from passing DNA material from one generation to the next
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4
Q

Crucial Function of Cell Division

A

distribution of identical genetic material from one parent cell to two daughter cells

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5
Q

Functions of Cell Division

A

1) asexual reproduction
2) renewal and repair (tissue)
3) growth and development

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6
Q

Cellular Organization of Genetic Material

A
  • all of the cell’s genetic material is its genome
  • a genome can consists of a single DNA molecule (most common in prokaryotic cells) or a number of DNA molecules (common in eukaryotic cells)
  • DNA molecules are densely condensed into chromosomes
  • found in eukaryotic cells, chromatin is a matrix that consists of DNA and proteins that condenses during cell division;
    -every eukaryotic species has a particular number of chromosomes in its cell’s nucleus
    -somatic cells (nonreproductive) have two sets of chromosomes
    -gametes (reproductive cells) have half as many chromosomes as somatic cells
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7
Q

Distribution of Chromosomes during Eukaryotic Cell Division

A
  • in preparation of cell division, DNA is replicated and chromosomes condense
  • each duplicated chromosome has two sister chromatids joined together by a centromere and attached by cohesins; they are joined copies of the original chromosome
    -the centromere is a joined of the duplicated chromosome where the two sister chromatids are most closely attached
    -during cell division the two chromatids separate and move to opposite sides of cell and later on into two different nuclei
    -once separate the two chromatids are called the chromosomes
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8
Q

Eukaryotic Cell Division

A

Mitosis and Cytokinesis

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9
Q

Mitosis

A

Division of genetic material in the nucleus

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10
Q

Cytokinesis

A

division of cytoplasm

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11
Q

Meiosis

A

yields nonidentical daughter cells with half as much genetic material as the parent cell;
produces gametes (reproductive cells)

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12
Q

Phases of Cell Cycle

A
  • interphase (cell growth and development; DNA replication)
  • mitotic (M) phase (cell division: mitosis and cytokinesis)
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13
Q

Interphase

A

accounts for 90% of the cell cycle and can be divided into three phases:
1) G1 (first growth/ first gap; metabolic activity and growth)
2) S (synthesis; DNA replication; involves metabolic activity and growth)
3) G2 (second growth; second gap; metabolic activity, cell growth and preparation for cell division)

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14
Q

Mitosis

A

distribution of chromosomes into two daughter nuclei;
it can be broken down into 5 stages:
1) prophase (getting organized part 1)
2) prometaphase (getting organized part 2)
3) metaphase (lining up)
4) anaphase (separating)
5) telophase (cleaning up)

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15
Q

Cytokinesis

A

separation of cells that entails division of cytoplasm that produces two daughter cells (each one with its own nucleus);
each cell can start a new cell cycle

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16
Q

Prophase

A

first stage in mitosis and meiosis;
DNA has already been replicated during interphase;
during this phase nucleolus disappears and chromatin reticulum condenses

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17
Q

Prometaphase

A

phase of mitosis following prophase and preceding metaphase;
it is characterized by disappearance of the nuclear envelope and formation of small membrane vesicles;
during this stage chromosomes form protein structures, called kinetochores;
kinetochore microtubules extend from centrosomes towards centromeres of chromosomes, throwing chromosomes in agitated motion;
other microtubules extend from opposing polar ends of the cell towards each other (even overlapping)

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18
Q

Metaphase

A

phase of mitosis, at which chromosomes are at their second most condensed form (first most is during anaphase);
chromosomes (containing genetic information) align the equator of cell;
centromeres are located along an equidistant from opposing sides metaphase plate;
they are held in place by kinetochore microtubules;
this phase accounts for 4 % of cell cycle;
the alignment is due to counterbalance of pulling forces of opposing kinetochore microtubules

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19
Q

Anaphase

A

stage of mitosis that separates the newly replicated chromosomes into opposite sides of cell;
chromosomes are at their most condensed form during late anaphase to help with segregation of chromosomes and nucleus reformation

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20
Q

Telophase

A

final stage of both mitosis and meiosis; reverses the functions of prophase and prometaphase;
once the chromosomes are at opposite sides of cells, a nuclear envelope reassembles;
chromosomes recondense and return back to its expanded chromatin that is present during interphase;
the mitotic spindle disassembles and the microtubules are depolymerized;
accounts for 2% of cell cycle’s duration

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21
Q

Mitotic Spindle

A

a structure made up of microtubules that control chromosome movement during mitosis;
in animal cells, microtubules begin in centrosomes (microtubule organizing center);
the centrosome replicates during interphase and migrates to opposing sides of cell during prophase and prometaphase;
an aster is a radial array of microtubules extending from a centrosome

22
Q

Kinetochore

A

each sister chromatid has a kinetochore;
during prometaphase kinetochores are formed by chromosomes;
they are attached to polar spindles by kinetochore microtubules;
at metaphase, centromeres are aligned the center of the cell (metaphase plate)

23
Q

Separase

A

an enzyme that cleaves cohesins of sister chromatids;
sister chromatids are separated when they begin to move along kinetochore microtubules towards opposing sides of polar spindles;
microtubule is polymerized at its end

24
Q

Results of a clever experiment

A

motor proteins “walk” sister chromatids along the kinetochore microtubules;
by pac-man effect, kinetochore microtubules shorten after motor proteins have moved the chromatins passed an area;
other research shows that chromosomes are “reeled in”;
general consensus: both are true

25
Q

Cytokinesis

A

In animal cells, cytokinesis occurs by cleavage;
the first sign of it is cleavage furrow, a shallow groove in cell surface that is formed where the metaphase plate was;
in plant cells, a cell plate forms

26
Q

Binary Fission

A

asexual reproduction of prokaryotes (bacteria and archae);
DNA begins to replicate at origin of replication;
two daughter chromosomes are formed;
they move toward opposite sides of cell;
a membrane pinches inward;
the cell is separated into two;
how bacterial chromosomes move and their location are active areas for research

27
Q

Evolution of Mitosis

A

because eukaryotes evolved from prokaryotes, mitosis evolved from binary fission;
certain unicellular eukaryotes exhibit cell division that is intermediate between binary fission and mitosis

28
Q

The Eukaryotic Cell Cycle is Regulated by a Molecular Control System

A
  • the frequency of the cell cycle varies by the type of cell
  • these differences result from regulation at the molecular level
  • cancer cells manage to escape the regular cell cycle control system
29
Q

Th Cell Cycle Control System

A

-the cell cycle seems to be driven by molecular signals from the cytoplasm
-this was found in an experiment conducted that used two different cultured mammalian cells going through different phases of cell cycle;
their nuclei were inserted into one of cells;
both started the phase that cytoplasm of the cell signaled to enter

30
Q

The cell cycle control system

A

A distinct control center that directs the sequential events of the cell cycle;
It’s checkpoints are subject to both internal and external regulation;
This control system proceeds on its own;
It is driven by a built-in clock;
Cannot proceed to the next phase until a go-ahead signal ir received

31
Q

Cyclin and Cyclin-Dependent Kinases (CDKs)

A

Regulatory proteins involved in cell cycle control

32
Q

Cyclins

A

Regulatory proteins involved in cell cycle regulation;
Are named for fluctuating concentrations in the cell

33
Q

Cyclin-Dependent Kinases

A

Regulatory proteins involved in cell cycle control system;
Their activity rises and falls with changes in concentration of its cyclin partner;
They must be attached to cyclins to be active;

34
Q

MPF (Maturation Promoting Factor)

A

A cyclin-CDK complex that triggers a cell’s passage past the G2 checkpoint into the M phase;
It’s peaks correspond to peaks of cyclin concentration;
They act as kinases while also activating other kinases indirectly

35
Q

Three checkpoints of Cell Cycle Control System

A

G1 (near end), G2 (near end), M (middle)

36
Q

Molecular Control of the Cell Cycle at the G2 Checkpoint

A
  • Synthesis of cyclin begins at S phase and continues through G2 phase, accumulating
  • Cyclin combines with CDKs, producing MPF. When enough MPFs accumulates, the cell passes the G2 checkpoint
  • MPF promotes mitosis through phosphorylation of various proteins;
    MPF’s activity peaks during metaphase
  • During anaphase, the cyclin component of MPF is degraded, terminating mitosis;
    The cell enters G1 phase
  • During G1 phase, degradation of cyclin continues as CDK is recycled
37
Q

Stop and Go Signals

A

-many registered signals at checkpoints come from cellular surveillance mechanisms within the cell
-checkpoints also register signals from outside of cell
-important checkpoints: G1, G2, M
- for many cells, G1 seems to be most important
-if cells passes this checkpoint, it will complete the cycle and divide
-if the cell does not receive the go-ahead signal at G1 it will not enter the cycle, it will enter a non-dividing phase, G0
- an example of an internal signal: a cell will not enter anaphase until all the chromosomes are properly aligned at the metaphase plate
-

38
Q

External Factors that Influence Cell Division

A

can be chemical or physical;
growth factors released by certain cells that stimulate others to divide;
platelet-derived growth factor (PDGF) is released by platelets (red blood cell fragments);
PDGF is required for division of cultured fibroblasts

39
Q

Go Phase

A

If a cell does not receive a Go-ahead signal at G1 it enters this nondividing state

40
Q

Growth factor

A

an external stimulus that a cell receives from another that stimulates cell division

41
Q

PDGF (Platelet-derived growth factor)

A

released by platelets (fragments of red blood cells) that is required for division of cultured fibroblasts

42
Q

Density-dependent inhibition

A

a type of regulation of cell division that occurs when crowded cells stop dividing

43
Q

Anchorage Dependence

A

a type of regulation of cell division;
to divide, cells must be attached to a substratum

44
Q

Behavior of cancer cells (regulation)

A

cancer cells do not exhibit density-dependent inhibition or anchorage dependence

45
Q

Two types of cell division regulation

A

density-dependent inhibition and anchorage dependence;
they check the growth of cells at optimal density

46
Q

Loss of Cell Cycle Controls in Cancer Cells

A

-cancer cells do not heed the normal signals that regulate the cell cycle
-they do not stop dividing once the growth factors are depleted
-cancer cells do not need growth factors to divide: a) they make their own growth factor
b) they may convey a growth factor signal without the presence of the growth factor
c) they may have an abnormal cell cycle control system
-cells that have acquired the ability to divide indefinitely have undergone transformation
-cancer cells that are not eliminated by the immune system form tumors (masses of abnormal cells within otherwise normal tissue)
-localized tumors can be treated with high energy radiation to damage DNA in cancer cells
-the majority of cancer cells have lost the ability to repair DNA damage

47
Q

Tumors

A

masses of abnormal cancer cells in otherwise normal tissue

48
Q

Benign Tumor

A

a lump of cancerous cells that is localized in its original site;
do not cause serious problems depending on their location

49
Q

Malignant Tumor

A

tumors that invade surrounding tissues;
they can undergo metastasis (the spread of cancer cells to other parts of the body where they may form additional tumors

50
Q

Metastasis

A

the spread of cancer cells to other parts of the body where additional tumors can be formed

51
Q

The Growth and Metastasis of Abnormal/ Malignant Cells in Breast Cancer

A

-tumor growth from a single cell
-cancer cells invade neighboring tissue
-cancer cells spread through lymph and blood vessels to other parts of the body
-a small percentage of cells may metastasize to another part of the body

52
Q

Treatment of Metastatic Tumors

A

-metastatic cells are treated with chemotherapy that target the cell cycle of cancerous cells
-side effects of chemotherapy are from the effect the drugs have on normal cells that divide frequently
-researchers are producing a flood of information about the cell-signaling pathways and their relationship to cancer
- coupled with new molecular techniques, treatment is becoming more personalized to a particular tumor

Fall 2023 (14 decks)

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