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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
Cytokinesis
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
Binary Fission
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
Evolution of Mitosis
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
The Eukaryotic Cell Cycle is Regulated by a Molecular Control System
- 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
Th Cell Cycle Control System
-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
The cell cycle control system
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
Cyclin and Cyclin-Dependent Kinases (CDKs)
Regulatory proteins involved in cell cycle control
32
Cyclins
Regulatory proteins involved in cell cycle regulation; Are named for fluctuating concentrations in the cell
33
Cyclin-Dependent Kinases
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
MPF (Maturation Promoting Factor)
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
Three checkpoints of Cell Cycle Control System
G1 (near end), G2 (near end), M (middle)
36
Molecular Control of the Cell Cycle at the G2 Checkpoint
- 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
Stop and Go Signals
-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
External Factors that Influence Cell Division
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
Go Phase
If a cell does not receive a Go-ahead signal at G1 it enters this nondividing state
40
Growth factor
an external stimulus that a cell receives from another that stimulates cell division
41
PDGF (Platelet-derived growth factor)
released by platelets (fragments of red blood cells) that is required for division of cultured fibroblasts
42
Density-dependent inhibition
a type of regulation of cell division that occurs when crowded cells stop dividing
43
Anchorage Dependence
a type of regulation of cell division; to divide, cells must be attached to a substratum
44
Behavior of cancer cells (regulation)
cancer cells do not exhibit density-dependent inhibition or anchorage dependence
45
Two types of cell division regulation
density-dependent inhibition and anchorage dependence; they check the growth of cells at optimal density
46
Loss of Cell Cycle Controls in Cancer Cells
-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
Tumors
masses of abnormal cancer cells in otherwise normal tissue
48
Benign Tumor
a lump of cancerous cells that is localized in its original site; do not cause serious problems depending on their location
49
Malignant Tumor
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
Metastasis
the spread of cancer cells to other parts of the body where additional tumors can be formed
51
The Growth and Metastasis of Abnormal/ Malignant Cells in Breast Cancer
-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
Treatment of Metastatic Tumors
-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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