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1

A distinguishing characteristic of living things from nonliving things

the ability of organisms to reproduce

2

the continuity of life is based upon...

the reproduction of cell, or cell division

3

Unicellular organisms

reproduce an entire organism by cell division

i.e. amoeba

4

Multicellular organisms

depend on cell division for multiple processes including: development from a fertilized cell or egg, growth of cells to develop tissues, and repair and renew cells that die from normal wear and tear or accidents

5

3 reasons for Mitosis to occur

1) Reproduction
2) Growth and development
3) Tissue renewal

6

Cell division is

part of the cell cycle

7

Cell cycle

the life of a cell from its origin in the division of a parent cell until its own division into two new cells

8

Cell division requires

the distribution of identical genetic material -- DNA - to 2 daughter cells

9

Cells duplicate their genetic material

before they divide, ensuring that each daughter cell receives an exact copy of the genetic material, DNA

10

Genome

(a cell's endowment of DNA, its) genetic information

can range from a single DNA molecule (prokaryotes) to several DNA molecules (eukaryotes)

11

DNA molecules in a cell are packaged into

chromosomes

12

(Eukaryotic) Chromosomes

have a characteristic number in each nucleus depending on the species and consist of chromatin

13

Chromatin

a complex of DNA and protein that condenses during cell division

14

in animals, somatic cells...

have two sets of chromosomes

-i.e. human somatic cells have 46 chromosomes (2 sets of 23 from each parent)

15

in animals, gametes

have one set of chromosomes

16

In preparation for cell division, DNA...

is replicated and the chromosomes condense to make a small package

17

Each duplicated chromosome has...

2 sister chromatids, which separate during cell division and contain identical DNA

18

During Condensation (of cell division)

the chromatids are connected at a narrow area, called the centromere

19

Centromere

narrow area at which the chromatids are connected

20

Later in cell division,

the chromatids are pulled apart into the new nuclei at opposite ends of the parent cell to form individual chromosomes

21

Eukaryotic cell division consists of

mitosis

22

mitosis

the division of the nucleus (karyokinesis), cytokinesis, and maintenance of the chromosome number

23

Karyokinesis

the division of the nucleus

24

Cytokinesis

the division of the cytoplasm

25

Meiosis

sex cells (gametes) have a reduction in chromosome number

- yield 4 nonidentical daughter cells

- each with half the chromosomes of the parent

26

Cell cycle

consists of the mitotic (M) phase which alternates with the longer interphase

27

mitotic phase is made up of

karyokinesis and cytokinesis

28

Interphase

the cell grows and prepared for cell division

divided into sub-phases: G1, S, and G2
G = growth phases
S = DNA synthesis (replication)

29

5 distinct phases or steps in mitosis

1) Prophase
2) Prometaphase
3) Metaphase
4) Anaphase
5) Telophase (and cytokinesis)

30

Prophase

the chromosomes are tightly packed, chromatids are joined, and the mitotic spindle begins to form

31

Prometaphase

the nuclear envelope fragments, the microtubules from the spindle interact with the chromosomes, and the chromatids contain a kinetochore

32

Metaphase

sister chromatids are arranged at the metaphase plate

33

Metaphase plate

an imaginary plane equidistant from the poles of the cell

34

Anaphase

the centromeres divide separating the sister chromatids which are pulled toward the poles

35

Telophase

daughter nuclei begin to form at the 2 poles and nuclear envelopes begin to arise

36

Mitotic Spindle

an apparatus of spindle microtubules and asters that controls chromosome movement during mitosis and arises from the centrosomes

soem spindle microtubules attach to the kinetochores of chromosome and move the chromosomes to the metaphase plate

37

In animal calls, Cytokinesis

follows mitosis (karyokinesis) and occurs by a process known as cleavage, which first appears by forming a cleavage furrow in the cell surface near the metaphase plate

Within the cytoplasm, is a contractile ring of actin microfilaments that facilitates and pinches the cell in two

38

Prokaryotes (bacteria) reproduce by a types of cell division called...

binary fission
(typically more rapid than in eukaryotes)

39

During binary fission,

the bacterial chromosome, which is circular DNA, replicates and the 2 daughter chromosomes actively move apart

1) Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell

2) Replication continues. One copy of the origin is now at each end of the cell

3) Replication finishes. The plasma membrane grows inward, and new cell wall is deposited

4) 2 daughter cells result

40

Regulation of Cell Cycle

the timing and rates of cell cycle division is crucial for normal growth and development of an organism

and is carefully regulated by an exquisite molecular control system

41

Frequency of cell division

varies among cell types and the molecules and enzymes present in the cytoplasm also regulate progress through the cell cycle

42

The sequential events of the cell cycle are directed by a

distinct cell cycle control system
(similar to a clock) with cyclinally operating enzymes to coordinate the cell cycle

43

The clock has

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

44

The signals are transmitted by..

signal transduction pathways with three major checkpoints in the G1, G2, and M phases

i.e. EGF (epidermal growth factor)

45

G1 checkpoint

restriction point
the most important

46

p53

is a tumor suppressor
- protein
- regulated gene
- cell health indicator: detect mutations

mutated p53 can cause cancer

47

Internal and External signals

control the cell cycles checkpoints:

1) Growth factors: stimulate other cells to divide (i.e. EGF)

2) Density-dependent inhibition: over-crowded cells stop dividing

3) most animal cells exhibit Anchorage Dependence in which they must be attached to a substratum to divide (i.e. EGF)

48

Cancer cells

do not respond normally to the body's control mechanisms and form tumors

exhibit neither dentist-dependent inhibition nor anchorage dependence

overgrowth leads to tumors and anchorage-independence results in Metastasis (spreading)

can form clump of overlapping cells

49

Malignant Tumor

invade surrounding tissues and can metastasize exporting cancer cells to other parts of the body where they may form secondary tumors