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Flashcards in Chapter 12 Deck (95):
1

The ability of organisms to produce more of their own kind best distinguishes living things from

nonliving matter

2

The continuity of life is based on the reproduction of cells, or

cell division

3

In unicellular organisms,

division of one cell reproduces the entire organism

(asexual reproduction)

4

Multicellular organisms depend on cell division for

growth and development, and repair

5

3 key roles of Mitosis

1. asexual reproduction
2. growth and development
3. repair

6

Cell division is an integral part of the cell cycle,

the life of a cell from formation to its own division

7

Mitosis-

dividing of DNA in the nucleus

8

Most cell division results in

daughter cells with identical genetic information, DNA

9

The exception is meiosis,

a special type of division that can produce sperm and egg cells

10

Cytokinesis

dividing the cytoplasm

11

All the DNA in a cell constitutes the cell's

genome

12

A genome can consist of

a single DNA molecule (common in prokaryotic cells) or a number of DNA molecules (common in eukaryotic cells)

13

DNA molecules in a cell are packaged into

chromosomes

14

Eukaryotic chromosomes consist of a chromatin,

a complex of DNA and protein that condenses during cell division

15

Every eukaryotic species has a characteristic number of

chromosomes in each cell nucleus.

Humans have 46

16

Somatic cells (nonreproductive cells)

have two sets of chromosomes
called diploid cells; 2n

17

Gametes (reproductive cells: sperm and eggs)

have half as many chromosomes as somatic cells
called haploid cells; n

18

Somatic Cells

body cell
2 sets of chromosomes
diploid
2n
2n=46

19

Gametic Cells

egg/sperm (germ)
1 set of chromosomes
haploid
n

20

In preparation for cell division,

DNA is replicated and the chromosomes condense

21

Each duplicated chromosome has

two sister chromatids (joined copies of the original chromosome), which separate during cell division

22

The centromere is the

narrow "waist" of the duplicated chromosome, where the two chromatids are most closely attached

23

During cell division,

the two sister chromatids of each duplicated chromosome separate and move into two nuclei

24

Sister chromatids ONLY exist as

sisters

25

Once separate, the (sister?) chromatids are called

chromosomes

26

Eukaryotic cell division consists of

Mitosis
and
Cytokinesis

27

Mitosis

the division of the genetic material (DNA) in the nucleus

28

Cytokinesis

the division of the cytoplasm

29

Gametes are produced by a

variation of cell division called meiosis

30

Meiosis yields nonidentical daughter cells that have only

one set of chromosomes, half as many as the parent cell

Humans 2n=46 to n=23

31

The mitotic phase alternates with

interphase in the cell cycle

32

Interphase (about 90% of the cell cycle) can be divided into subphases

G1 phase ("first gap")
S phase ("synthesis")
G2 phase ("second gap")

33

The cell grows during all three phases, but

chromosomes are duplicated only during the S phase

34

Mitosis is conventionally divided into five phases

P- Prophase
P- Prometaphase
M- Metaphase
A- Anaphase
T- Telophase

35

Prophase

chromosomes become visible

36

Prometaphase

nuclear envelope disappears/ spindle fibers attach to kintochore (DNA)

37

Metaphase

line up

38

Anaphase

pull apart

39

Telophase

nuclear envelope reforms, goes back to chromatin

40

Cytokinesis overlaps the

latter stages of mitosis

41

The mitotic spindle is a structure made of

microtubules that controls chromosome movement during mitosis

42

In animal cells, assembly of spindle microtubules begins in the

centrosome, the microtubule organizing center

43

The centrosome replicates during interphase (G2 phase), forming

two centrosomes that migrate to opposite ends of the cell during prophase and prometaphase

44

An aster (a radial array of short microtubules)

extends from each centrosome

45

The spindle includes the

centrosomes, the spindle microtubules, and the asters

46

During prometaphase,

some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes

47

Kinetochores are

protein complexes associated with centromeres

48

At metaphase,

the chromosomes are lined up at the metaphase plate, an imaginary structure at the midway point between the spindle's two poles

49

In anaphase,

sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell.

Proteins holding together sister chromatids are suddenly inactivated

50

The microtubules shorten by

depolymerizing at their kinetochore ends.

Motor proteins on a kinetochore "walk" a chromosome along a microtubule toward the nearest pole

51

Nonkinetochore microtubules from opposite poles overlap and

push against each other, elongating the cell. (stretches the cell).

(They don't grab onto the DNA, but they are really important)

52

In telophase,

genetically identical daughter nuclei form at opposite ends of the cell

53

Cytokinesis beings during

anaphase or telophase and the spindle eventually disassembles.

54

Cytokinesis is NOT part of

Mitosis.

They just overlap a bit sometimes.

55

In animal cells, cytokinesis occurs by a process known as

cleavage, forming a cleavage furrow.

56

Cleavage furrow is

a contractile ring of actin and microfilaments myosin protein.
Like a drawstring pulling it tight, until it pops apart.

57

Cytokinesis in animal cells

cleavage- process
cleavage furrow- structure formed

58

In plant cells, cytokinesis occurs by a process known as

cell plate formation, which forms a cell plate

59

A cell plate is

specialized vesicles grown and then fuse

60

Cytokinesis in plant cells

cell plate formation- process
cell plate- structure formed

61

Prokaryotes (bacteria and archaea) reproduce by a type of cell division called

binary fission

62

In binary fission,

the chromosome replicates (beginning at the origin of replication), and the two daughter chromosomes actively move apart.

63

Prokaryotes do NOT have any

mitotic spindles or microtubules that direct this traffic (replication, binary fission)

64

In binary fission, the plasma membrane

pinches inward, dividing the cell into two

65

The Eukaryotic cell cycle is regulated by a

molecular control system

66

The frequency of cell division varies with the

type of cell.

These differences result from regulation at the molecular level.

67

Cancer cells manage to

escape the usual controls on the cell cycle

68

The cell cycle appears to be driven by

specific chemical signals present in the cytoplasm.

(a specific chemical signal is the reason a cell divides)

69

The sequential events of the cell cycle are directed by a distinct

cell cycle control system, which is similar to a clock

70

The cell cycle control system is regulated by

both internal and external controls

71

The clock (cell cycle) has specific checkpoints where

the cell cycle stops until a go-ahead signal is received

72

For many cells, the G1 checkpoint seems to be

the most important

73

If a cell receives a go-ahead signal at the G1 checkpoint, it will usually

complete the S, G2, and M phases and divide

74

If the cell cycle does not receive the go-ahead signal at the G1 checkpoint, it

will exit the cycle, switching into a non-dividing state called the G0 phase.

75

In the G0 phase,

cells will never divide again.

76

Two types of regulatory proteins are involved in cell cycle control:

Cyclins
and
Cyclin-dependent kinases (Cdks)

77

Cyclin-dependent kinases (Cdks) activity fluctuates during the cell cycle because it is

controlled by cycles, so named because their concentrations vary with the cell cycle

78

MPF (maturation-promoting factor) is a

cyclin-Cdk complex that triggers a cell's passage past the G2 checkpoint into the M phase

79

Cyclin is what is

cycling and is around sometimes but not always
(??)

80

Cyclin is really high during the

G2 and M phase, so cyclin-dependent kinases works best at the G2 and M phase too.

81

An example of an internal signal is that

kinetochores not attached to spindle microtubules send a molecular signal that delays anaphase

82

Some external signals are

growth factors (paracrine signaling), proteins released by certain cells that stimulate other cells to divide

83

For example, platelet-derived growth factor (PDGF) stimulates the division of

human fibroblast cells in culture.
(have to have PDGF if want a cell to divide??)

(external signal?)

84

A clear example of external signals is

density-dependent inhibition, in which crowded cells stop dividing.

(As soon as things become dense, packed, crowded, and full, the cells stop dividing.

85

Most animal cells also exhibit

anchorage dependence, in which they must be attached to a substratum in order to divide

(has to be stuck to something in order to divide)

86

Cancer cells exhibit neither

density-dependent inhibition nor anchorage dependence.

(cancer cells just divide and don't obey those two things. They don't need any signals or growth factors.)

87

Cancer cells do not respond normally to the

body's control mechanisms

88

HeLa cells

"immortal cell line"

89

Cancer cells may not need growth factors to grow and divide.

-They may make their own growth factor.
-They may convey a growth factor's signal without the presence of the growth factor.
-They may have an abnormal cell cycle control system.

90

A normal cell is converted to a cancerous cell by a process called

transformation

91

Cancer cells that are not eliminated by the immune system form

tumors, masses of abnormal cells within otherwise normal tissue

92

If abnormal cells remain only at the original site, the lump is called a

benign tumor

93

Malignant tumors invade

surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form additional tumors.

(Malignant tumors grow bigger and bigger. They are really bad)

94

Recent advantages in understanding the cell cycle and cell cycle signaling have led to

advances in cancer treatment

95

Cancer results from

genetic changes that affect cell cycle control