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Chapter 9. MITOSIS (CELL DIVISION) AND CELL CYCLE. Activator— kwl chart mitosis. activator. Name the stages of mitosis in order. Impacts, Issues: Henrietta’s Immortal Cells. Cancer cells isolated from Henrietta Lacks established a self-perpetuating lineage of cancer cells

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Chapter 9

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Chapter 9

Chapter 9

MITOSIS (CELL DIVISION) AND CELL CYCLE


Activator kwl chart mitosis

Activator—kwl chart mitosis


Activator

activator

Name the stages of mitosis in order.


Impacts issues henrietta s immortal cells

Impacts, Issues: Henrietta’s Immortal Cells

  • Cancer cells isolated from Henrietta Lacks established a self-perpetuating lineage of cancer cells

  • The cell lineage, name HeLa cells, is used in research laboratories across the world

  • Henrietta Lacks’ contribution is used to research cancer, viral growth, protein synthesis, effects of radiation, and more


Chapter 9

Henrietta’s Immortal Cells

Fig. 9-2, p.141


Understanding cell division

Understanding Cell Division

  • “Omnis cellula e cellula”---ALL cells from cells

  • What instructions are necessary for inheritance?

  • How are those instructions duplicated for distribution into daughter cells?

  • By what mechanisms are instructions parceled out to daughter cells?


Reproduction

Reproduction

  • Parents produce a new generation of cells or multicelled individuals like themselves

  • Parents must provide daughter cells with hereditary instructions, encoded in DNA, and enough metabolic machinery to start up their own operation


Division mechanisms

Division Mechanisms

Eukaryotic organisms

  • Mitosis(nuclear division) & cytokinesis (cytoplasm division)

  • Meiosis—ch 10

    Prokaryotic organisms

  • Prokaryotic fission—replicates only a small, single, circular chromosome


Human life cycle

HUMAN LIFE CYCLE


Bozeman video mitosis

Bozeman Video--Mitosis

http://www.youtube.com/watch?v=1cVZBV9tD-A


Roles of mitosis

Roles of Mitosis

  • Multicelled organisms

    • Growth

    • Cell replacement

  • Some protistans, fungi, plants, animals

    • Asexual reproduction


Cell division

Cell Division

  • Individual cells of a human embryo divide, developing from a paddlelike structure into a hand


Chapter 9

Cell Division

Fig. 9-10, p.149


Chromosome

Chromosome

  • A DNA molecule & attached proteins

  • Duplicated in preparation for mitosis

onechromosome (unduplicated)

one chromosome (duplicated)


Chapter 9

Chromosome

a One chromosome (unduplicated)

onechromatid

two sister

chromatids

onechromatid

b One chromosome (duplicated)

Stepped Art

Fig. 9-3a, p.142


Structure of chromosome pair

Structure of chromosome pair

  • Sister chromatids

  • Centromere

  • locus


Organization of chromosomes

Organization of Chromosomes

DNA

one nucleosome

DNA and proteins

arranged as cylindrical fiber

histone


Chromosome number

Chromosome Number

  • Sum total of chromosomes in a cell

  • Somatic cells

    • Chromosome number is diploid (2n)

    • Two of each type of chromosome

  • Gametes

    • Chromosome number is haploid (n)

    • One of each chromosome type


The cell cycle alternates between m mitosis phase and interphase

The Cell Cycle—alternates between m (mitosis) phase and interphase

interphase

G1

S

telophase

anaphase

Mitosis

G2

metaphase

prophase

Figure 9.5Page 144


Interphase

Interphase

  • Usually longest part of the cycle

  • Nondividing phase

  • Cell increases in mass (grows & PREPARES for division)

  • Number of cytoplasmic components doubles

  • DNA is duplicated


Chapter 9

  • G1—1st growth phase

  • S– synthesis (DNA replicates)

  • G2– 2nd growth phase; considered by some to be the first phase of mitosis


Mitosis

Mitosis

  • Period of nuclear division

  • Usually followed by cytoplasmicdivision(cytokinesis)

  • Four stages:

    Prophase

    Metaphase

    Anaphase

    Telophase


Control of the cycle

Control of the Cycle

  • Once S begins, the cycle automatically runs through G2 and mitosis

  • The cycle has a built-in molecular brake in G1

  • Cancer involves a loss of control over the cycle, malfunction of the “brakes”


Stopping the cycle

Stopping the Cycle

  • Some cells normally stop in interphase

    • Neurons in human brain

    • Arrested cells do not divide

  • Adverse conditions can stop cycle

    • Nutrient-deprived amoebas get stuck in interphase


The spindle apparatus

The Spindle Apparatus

  • Consists of two distinct sets of microtubules

    • Each set extends from one of the cell poles

    • Two sets overlap at spindle equator

  • Moves chromosomes during mitosis


Spindle apparatus

Spindle Apparatus

one spindle pole

one of the condensed chromosomes

spindle equator

microtubules organized

as a spindle apparatus

one spindle pole


Maintaining chromosome number

chromosome (unduplicated) in cell at interphase

same chromosome (duplicated) in interphase prior to mitosis

mitosis, cytoplasmic division

chromosome (unduplicated)

in daughter cell

at interphase

chromosome (unduplicated)

in daughter cell

at interphase

Maintaining Chromosome Number


Maintaining chromosome number1

Maintaining Chromosome Number

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

XX (or XY)

Fig. 9-6a, p.145


Chapter 9

Maintaining Chromosome Number

b The same two

hromosomes, now

duplicated, in that

cell at interphase,

prior to mitosis

c

a Two of the chromosomes

(unduplicated)

in a parent cell at interphase

c Two chromosomes

(unduplicated) in the

parent cell’s daughter

cells, which both start

life in interphase

Fig. 9-6b, p.145


Chapter 9

pole

Maintaining Chromosome Number

pole

microtubule of

bipolar spindle

p.145


Stages of mitosis

Stages of Mitosis

Prophase

Metaphase

Anaphase

Telophase


Early prophase mitosis begins

Early Prophase - Mitosis Begins

Duplicated chromosomes begin to condenseand become observable under a microscope; mitotic spindle

forms

Figure 9.7

Page 146


Late prophase aka prometaphase

Late Prophase—AKA Prometaphase

  • New microtubules are assembled

  • One centriole pair is moved toward opposite pole of spindle

  • Nuclear envelope starts to break up

Figure 9.7

Page 146


Transition to metaphase

Transition to Metaphase

  • Spindle forms

  • Spindle microtubules become attached to the two sister chromatids of each chromosome

Figure 9.7

Page 146


Metaphase

Metaphase

  • All chromosomes are lined up at the spindle equator

  • Chromosomes are maximally condensed

Figure 9.7

Page 147


Anaphase

Anaphase

  • Characterized by MOVEMENT!

  • Sister chromatids of each chromosome are pulled apart thus elongating the cell

  • Once separated, each chromatid is a chromosome

  • Kinetechore vs. nonkinetechoremicrotubles

Figure 9.7

Page 147


Telophase

Telophase

  • Chromosomes loosen and become less distinct

  • Two nuclear membranes form, one around each set of unduplicated chromosomes

  • Cytokinesis starts to produce 2 identical daughter cells

  • Plasmodia—when some slime molds have NO cytokinesis resulting in mulitnucleated masses

Figure 9.7

Page 147


Results of mitosis

Results of Mitosis

  • Two daughter nuclei

  • Each with same chromosome number as parent cell

  • Chromosomes in unduplicated form

Figure 9.7

Page 147


Chapter 9

a Cell at Interphase

The cell duplicates its DNA, prepares for nuclear division

Mitosis

pair of centrioles

nuclear

envelop

chromosomes

b EARLY PROPHASE

c LATE PROPHASE

d TRANSITION TO METAPASE

Mitosis begins. The DNA and its associated proteins have started to condense. The two chromosomes color-coded purple were inherited from the female parent. The other two (blue) are their counterparts., inherited from the male parent.

Chromosomes continue to condense. New microtubules become assembled. They move one of the two pairs of centrioles to the opposite end of the cell. The nuclear envelope starts to break up.

Now microtubules penentrate the nuclear region. Collectively, they form a bipolar spindle apparatus. Many of the spindle microtubules become attatched to the two sister chromatids of each chromosome.

Fig. 9-7a, p.146


Chapter 9

microtubule

e METAPHASE

f ANAPHASE

g TELOPHASE

h INTERPHASE

All chromosomes have become lined up at the spindle equator. At this stage of mitosis (and of the cell cycle), they are most tightly condensed

Attachments between the two sister chromatids of each chromosome break. The two are separate chromosomes, which microtubules move to opposite spindle pores.

There are two clusters

of chromosomes, which decondense. Patches of new membrane fuse to form a new nuclear envelope. Mitosis is completed.

Now there are two daughter cells. Each is diploid; its nucleus has two of each type

of chromosome, just like the parent cell.

Fig. 9-7b, p.146


Chapter 9

Animal Cell Division—cleavage furrow forms at old metaphase plate by way of an actin contractile ring


Chapter 9

Animal Cell Division—

1 Mitosis is

over, and the spindle is now disassembling.

2 At the former spindle equator, a ring of micro-filaments attached to the plasma membrane contracts.

3As its diameter shrinks, it pulls the cell surface inward.

4Contractions continue; the cell is pinched in two.

Fig. 9-8a, p.148


Chapter 9

Cell Plate Formation

cell plane forming

1As mitosis ends, vesicles cluster at the spindle equator. They contain materials for anew primary cell wall.

2Vesicle membranes fuse. The wall material is sandwiched between two new membranes that lengthen along the plane of a newly forming cell plate.

3 Cellulose is deposited inside the sandwich. In time, these deposits will form two cell walls. Others will form the middle lamella between the walls and cement them together.

4A cell plate grows at its margins until it fuses with the parent cell plasma membrane. The primary wall of growing plant cells is still thin. New material—cellulose- is deposited on it.

Fig. 9-8b, p.148


Mitotic control

Mitotic Control

  • Growth factors—such as needed nutrients

  • Density-dependent inhibition—overcrowding=less growth

  • Checkpoint(restriction point)—Ex: cells have a checkpoint in G1 where cell can either go on with cycle or go into G 0 (this is where mature muscle and nerve cells are)


Continued mitotic control

CONTINUED MITOTIC CONTROL

  • CYCLIN-DEPENDENT KINASES-AKA Cdks

  • enzymes(proteins) which are affected by the cell cycle regulatory protein cyclin; when these enzymes are active & attached to cyclin, then mitosis can happen)

  • Ex: MPF (maturation promoting factor)


Cell cycle relative cyclin concentration

CELL CYCLE & RELATIVE CYCLIN CONCENTRATION


Tumors

Tumors

  • Sometimes a checkpoint gene mutates and control over cell division is lost.

  • Cells uncontrollable division forms an abnormal mass called a tumor.

  • Neoplasms


Chapter 9

Cancer

Fig. 9-12, p.150


Malignant vs benign see p 151

MALIGNANT VS. BENIGN (see p. 151)


Chapter 9

cell at interphase

nucleus

cytoplasm

telophase

prophase

metaphase

anaphase

Fig. 9-15, p.153


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