Chapter 9 ppt

(1)

Biology

Sylvia S. Mader

Michael Windelspecht

Chapter 9 The Cell Cycle and

Cellular

Reproduction

Lecture Outline

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(2)

Outline

• 9.1 The Cell Cycle

• 9.2 Mitosis and Cytokinesis

(3)

9.1 The Cell Cycle

• The

cell cycle

is an orderly set of stages

from the first division to the time the

resulting daughter cells divide

• Just prior to the next division:



The cell grows larger



The number of organelles doubles



The DNA is replicated

• The two major stages of the cell cycle:



Interphase

(includes several stages)

(4)

The Cell Cycle

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

G

1 (growth)

G

₀

G

2 checkpoint

Mitosis checkpoint.

Mitosis will occur

if DNA has

replicated properly.

Apoptosis will

occur if the DNA is

damaged and

cannot be repaired.

S

(growth and DNA

replication)

M

Interphase

G1 checkpoint

Cell cycle main checkpoint.

If DNA is damaged, apoptosis

will occur. Otherwise, the cell

is committed to divide when

growth signals are present

and nutrients are available.

M checkpoint

Spindle assembly

checkpoint. Mitosis

will not continue if

chromosomes are

not properly aligned.

M

G

2 G

1 G

₂

(growth and final

preparations for

(5)

The Cell Cycle

• Interphase



Most of the cell cycle is spent in

interphase



Cell performs its usual functions



Time spent in interphase varies by cell

type



Nerve and muscle cells do not

complete the cell cycle (remain in the

(6)

The Cell Cycle

• Interphase consists of: G

₁

, S, and G

₂

phases



G

₁

Phase:

• Recovery from previous division

• Cell doubles its organelles

• Cell grows in size

• Cell accumulates raw materials for DNA synthesis



S Phase:

• DNA replication

• Proteins associated with DNA are synthesized

• Chromosomes enter with 1

chromatid

each

• Chromosomes leave with 2 identical chromatids (

sister

chromatids

) each



G

₂

Phase:

(7)

The Cell Cycle

• M (Mitotic) Stage



Includes:

• Mitosis

– Nuclear division

– Daughter chromosomes are distributed by the

mitotic

spindle

to two daughter nuclei

• Cytokinesis

– Division of the cytoplasm



Results in two genetically identical daughter

(8)

The Cell Cycle

• The cell cycle is controlled by internal and

external signals

• A

signal

is a molecule that either stimulates or

inhibits a metabolic event.



Internal signals

• Family of proteins called

cyclins

that increase and

decrease as the cell cycle continues

• Without cyclins, the cell cycle stops at G

₁

, M or G

₂

(checkpoints)

(9)

The Cell Cycle

• Apoptosis

is programmed cell death

• It involves a sequence of cellular events:



fragmenting of the nucleus,



blistering of the plasma membrane



engulfing of cell fragments

.

• Apoptosis is caused by enzymes called

caspases.

• Mitosis and apoptosis are opposing forces



Mitosis increases cell number

(10)

Apoptosis

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apoptotic cell

cell

fragment

DNA

fragment

Cell rounds

up, and nucleus

collapses.

Chromatin

condenses, and

nucleus fragments.

Plasma membrane

blisters, and blebs

form.

Cell fragments

contain DNA

fragments.

blebs

(11)

The Cell Cycle

• Apoptosis



Cells harbor caspases that are kept in

check by inhibitors

• Can be unleashed by internal or external

signals



Signal protein

p53

• Stops the cell cycle at G

₁

when DNA is

damaged

• Initiates an attempt at DNA repair

–If successful, the cycle continues to

mitosis

(12)

Regulation at the G1

Checkpoint

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

a.

P

RB

protein

RB

protein

E2F

CDK

not present

E2F not released

released

E2F

E2F binds to DNA.

DNA

cell cycle

proteins

phosphorylated RB

CDK present

P

breakdown

of p53

no DNA

damage

DNA

damage

phosphorylated p53

DNA repair

proteins

apoptosis

p53 binds to DNA.

(13)

9.2 Mitosis and Cytokinesis

• DNA is in very long threads



Chromosomes



Stretched out and intertwined between divisions



DNA is associated with

histones

(proteins)



DNA and histone proteins are collectively called

chromatin

• Before mitosis begins:



Chromatin condenses (coils) into distinctly

visible chromosomes



Each species has a characteristic

(14)

(15)

Mitosis and Cytokinesis

• The

diploid

(2n)

number includes two sets

of chromosomes of each type



Humans have 23 different types of

chromosomes

• Each type is represented twice in each body cell

(diploid)

• Only sperm and eggs have one of each type

·termed

haploid (n)



The haploid (n) number for humans is 23

• Two representatives of each chromosome type

• Makes a total of 2n = 46 in each nucleus

(16)

Mitosis and Cytokinesis

• At the end of S phase:



Each chromosome internally duplicated



Consists of two identical DNA chains

• Sister chromatids (two strands of genetically identical

chromosomes)

• Attached together at a single point (called

centromere

)

• During mitosis:



Centromeres holding sister chromatids together

separate



Sister chromatids separate



Each becomes a daughter chromosome



Sisters of each type are distributed to opposite

(17)

Duplicated Chromosomes

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

centromere

sister chromatids

one chromatid

a.

b.

kinetochore

(18)

Mitosis and Cytokinesis

• Just outside the nucleus is the

centrosome



This is the microtubule organizing center in animal

cells



Organizes the mitotic spindle

• Contains many fibers

• Each fiber is composed of a bundle of microtubules



In animals, the centrosome contains two

barrel-shaped

centrioles

• Oriented at right angles to each other within the centrosome

• Each has 9 triplets of microtubules arranged in a cylinder

(19)

Mitosis and Cytokinesis

• Phases of Mitosis:



Prophase

• Chromatin has condensed

– Chromosomes are distinguishable with microscope

– Each chromosome has two sister chromatids attached at

the centromere

• Nucleolus disappears

• Nuclear envelope disintegrates

• Spindle begins to assemble

• The two centrosomes move away from each other

(20)

Mitosis and Cytokinesis

• Phases of Mitosis



Prometaphase

• The centromere of each chromosome

develops two kinetochores

– Specialized protein complex

– One attached to each sister chromatid

» Physically connect sister chromatids with specialized

microtubules (

kinetochores

)

(21)

Mitosis and Cytokinesis

• Stages of Mitosis



Metaphase

• Chromosomes are pulled around by kinetochore fibers

• Forced to align across the equatorial plane of the cell

–

Metaphase plate -

Represents plane through which

mother cell will be divided



Anaphase

• Centromere dissolves, releasing sister chromatids

• Sister chromatids separate

– Now called daughter chromosomes

(22)

Mitosis and Cytokinesis

• Stages of Mitosis



Telophase

• Spindle disappears

• Now two clusters of daughter chromosomes

– Still two of each type with all types represented

– Clusters are incipient daughter nuclei

• Nuclear envelopes form around the two

incipient daughter nuclei

(23)

Mitosis and Cytokinesis

• Cytokinesis = division of cytoplasm

• Allocates the mother cell’s cytoplasm equally to

daughter nucleus

• Encloses each daughter cell in its own plasma

membrane

• Often begins in anaphase

• Animal cytokinesis:



A

cleavage furrow

appears between daughter nuclei



Formed by a contractile ring of actin filaments



Like pulling on a drawstring

(24)

Mitosis and Cytokinesis

• Cytokinesis in plant cells begins with the formation of a

cell plate



Rigid cell walls outside plasma membrane do not

permit furrowing



Many small membrane-bounded vesicles



Eventually fuse into one thin vesicle extending across

the mother cell



The membranes of the cell plate become the plasma

membrane between the daughter cells



The space between the daughter cells becomes filled

with the middle lamella



Daughter cells later secrete primary cell walls on

(25)

Cytokinesis in Animal Cells

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cleavage furrow

Contractile ring

(26)

Cytokinesis in Plant Cells

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

daughter cells

nucleoli

daughter

nucleus

cell plate formation

daughter nucleus

vesicles containing

membrane components

fusing to form cell plate

(27)

Phases of Mitosis in Animal and

Plant Cells

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Animal cell(Early prophase, Prophase, Metaphase, Anaphase, Telophase): © Ed Reschke; Animal cell(Prometaphase): © Michael Abbey/Photo Researchers, Inc.;

Plant cell(Early prophase, Prometaphse): © Ed Reschke; Plant cell(Prophase, Metaphase, Anaphase): © R. Calentine/Visuals Unli mited; Plant cell(Telophase): © Jack M.

Bostrack/Visuals Unlimited;

Plant Cell at Interphase centromere aster kinetochore

polar spindle fiber

chromosomes cell wall 25µm centrosome lacks centrioles M IT O SI S centrosome has centrioles Animal Cell at Interphase nuclear envelope fragments chromatin condenses nucleolus disappears Early Prophase Centrosomes have duplicated. Chromatin is condensing into chromosomes, and the nuclear envelope is fragmenting.

Prophase Nucleolus has disappeared, and duplicated chromosomes are visible.

Centrosomes begin moving apart, and spindle is in process of forming.

Centrosomes begin moving apart, and spindle is in process of forming. 20 µm duplicated

chromosome 20 µm

spindle fibers forming

spindle pole 9 µm

kinetochore spindle fiber

cleavage furrow

spindle fibers

20µm 16µm

Anaphase Sister chromatids part and become daughter chromosomes that move toward the spindle poles. In this way, each pole receives the same number and kinds of chromosomes as the parent cell. Metaphase

Centromeres of duplicated chromosomes are aligned at the metaphase plate (center of fully formed spindle). Kinetochore spindle

fibers attached to the sister chromatids come from opposite spindle poles.

chromosomes at metaphase plate

6.2µm 6.2µm

20µm 6.2µm spindle pole lacks _{centrioles and aster}

Telophase

Daughter cells are forming

as nuclear envelopes and

nucleoli reappear. Chromosomes will

become indistinct chromatin.

daughter chromosome 20µm nucleolus

(28)

Phases of Mitosis in Animal and Plant Cells

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Early Prophase

aster

20 µm

25 µm

MIT

OSI

S

Early Prophase

Centrosomes have duplicated.

Chromatin is condensing into

chromosomes, and the nuclear

envelope is fragmenting.

chromatin

condenses

nucleolus

disappears

nuclear

envelope

fragments

Animal Cell

at Interphase

centrosome

has centrioles

centrosome

lacks centrioles

(29)

Phases of Mitosis in Animal and Plant Cells

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Animal cell(Early prophase, Prophase): © Ed Reschke; Plant cell(Early prophase): © Ed Reschke; Plant cell(Prophase): © R. Cal entine/Visuals Unlimited

Prophase

spindle

fibers forming

centromere

aster

chromosomes

cell wall

20 µm

6.2 µm

25 µm

Prophase

Nucleolus has disappeared, and

duplicated chromosomes are

visible. Centrosomes begin moving

apart, and spindle is in process

of forming.

MI

T

OSI

S

centrosome

lacks centrioles

Animal Cell

at Interphase

centrosome

has centrioles

nuclear

envelope

fragments

chromatin

condenses

nucleolus

disappears

Early Prophase

Centrosomes have duplicated.

Chromatin is condensing into

chromosomes, and the nuclear

envelope is fragmenting.

duplicated

chromosome

(30)

Phases of Mitosis in Animal and Plant Cells

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Animal cell(Early prophase, Prophase, Metaphase): © Ed Reschke; Animal cell(Prometaphase): © Michael Abbey/Photo Researchers, Inc.;

Plant cell(Early prophase, Prometaphse): © Ed Reschke; Plant cell(Prophase): © R. Calentine/Visuals Unlimited

Prometaphase

centromere

spindle

pole

aster

kinetochore

polar spindle fiber

chromosomes

cell wall

20 µm

6.2 µm

25 µm

20 µm

9 µm

Prometaphase

The kinetochore of each

chromatid is attached to a

kinetochore spindle fiber. Polar

spindle fibers stretch from each

spindle pole and overlap.

centrosome

has centrioles

Animal Cell

at Interphase

nuclear

envelope

fragments

chromatin

condenses

nucleolus

disappears

spindle

fibers forming

Early Prophase

Centrosomes have duplicated.

Chromatin is condensing into

chromosomes, and the nuclear

envelope is fragmenting.

Prophase

Nucleolus has disappeared, and

duplicated chromosomes are visible.

Centrosomes begin moving apart,

and spindle is in process of forming.

kinetochore

spindle fiber

duplicated

chromosome

(31)

Phases of Mitosis in Animal and Plant Cells

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Animal cell(Early prophase, Prophase, Metaphase): © Ed Reschke; Animal cell(Prometaphase): © Michael Abbey/Photo Researchers, Inc.;

Plant cell(Early prophase, Prometaphse): © Ed Reschke; Plant cell(Prophase, Metaphase): © R. Calentine/Visuals Unlimited

duplicated

chromosome

centromere

aster

kinetochore

polar spindle fiber

chromosomes

cell wall

20 µm

6.2 µm

25 µm

20 µm

9 µm

spindle fibers

20 µm

6.2 µm

Metaphase

Centromeres of duplicated

chromosomes are aligned at the

metaphase plate (center of fully

formed spindle). Kinetochore

spindle fibers attached to the

sister chromatids come from

opposite spindle poles.

centrosome

has centrioles

Animal Cell

at Interphase

nuclear

envelope

fragments

nucleolus

disappears

chromatin

condenses

centrosome

lacks centrioles

Early Prophase

Centrosomes have duplicated.

Chromatin is condensing into

chromosomes, and the nuclear

envelope is fragmenting.

Prophase

Nucleolus has disappeared, and

duplicated chromosomes are visible.

Centrosomes begin moving apart,

and spindle is in process of forming.

Prometaphase

The kinetochore of each chromatid is

attached to a kinetochore spindle fiber.

Polar spindle fibers stretch from each

spindle pole and overlap.

Metaphase

kinetochore

spindle fiber

chromosomes at

metaphase plate

spindle

pole

kinetochore

spindle fiber

spindle

fibers forming

Plant Cell

at Interphase

spindle pole lacks

centrioles and aster

(32)

Phases of Mitosis in Animal and Plant Cells

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Animal cell(Early prophase, Prophase, Metaphase, Anaphase): © Ed Reschke; Animal cell(Prometaphase): © Michael Abbey/Photo Researchers, Inc.;

Plant cell(Early prophase, Prometaphse): © Ed Reschke; Plant cell(Prophase, Metaphase, Anaphase): © R. Calentine/Visuals Unlimited

centromere spindle pole aster kinetochore kinetochore spindle fiber polar spindle fiber

chromosomes cell wall

20 µm 20 µm

6.2 µm

25 µm 20 µm

9 µm _{daughter chromosome}

spindle fibers

20 µm 20 µm

6.2 µm 6.2 µm centrosome has centrioles Animal Cell at Interphase nuclear envelope fragments nucleolus disappears chromatin condenses centrosome lacks centrioles Early Prophase Centrosomes have duplicated. Chromatin is condensing into chromosomes, and the nuclear envelope is fragmenting.

Prometaphase The kinetochore of each chromatid is attached to a kinetochore spindle fiber.

Polar spindle fibers stretch from each spindle pole and overlap.

Metaphase Centromeres of duplicated chromosomes are aligned at the metaphase plate (center of fully formed spindle). Kinetochore spindle

Anaphase chromosomes at

metaphase plate

spindle pole lacks centrioles and aster Plant Cell at Interphase duplicated chromosome spindle fibers forming

M

IT

OS

IS

Anaphase

(33)

Phases of Mitosis in Animal and Plant Cells

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

centromere aster

kinetochore

polar spindle fiber

chromosomes cell wall

20 µm 20 µm

6.2 µm

25 µm 20 µm

9 µm _{daughter chromosome}

spindle fibers cell plate

20 µm 20 µm 16 µm

6.2 µm 6.6 µm 6.2 µm

nucleolus

cleavage furrow

Telophase

Daughter cells are forming

as nuclear envelopes and

nucleoli reappear.

Chromosomes will

become indistinct chromatin.

centrosome has centrioles Animal Cell at Interphase nuclear envelope fragments chromatin condenses nucleolus disappears centrosome lacks centrioles Plant Cell at Interphase Early Prophase Centrosomes have duplicated. Chromatin is condensing into chromosomes, and the nuclear envelope is fragmenting.

spindle fibers forming

duplicated chromosome

kinetochore spindle fiber Prophase

Nucleolus has disappeared, and duplicated chromosomes are visible.

Prometaphase The kinetochore of each chromatid is attached to a kinetochore spindle fiber.

Polar spindle fibers stretch from each spindle pole and overlap.

Metaphase Centromeres of duplicated chromosomes are aligned at the metaphase plate (center of fully formed spindle). Kinetochore spindle

Anaphase Sister chromatids part and become daughter chromosomes that move toward the spindle poles. In this way, each pole receives the same number and kinds of chromosomes as the parent cell.

Telophase

spindle pole lacks centrioles and aster

spindle pole

chromosomes at metaphase plate

Animal cell(Early prophase, Prophase, Metaphase, Anaphase, Telophase): © Ed Reschke; Animal cell(Prometaphase): © Michael Abbey/Photo Researchers, Inc.; Plant cell(Early prophase, Prometaphse):

© Ed Reschke; Plant cell(Prophase, Metaphase, Anaphase): © R. Calentine/Visuals Unlimited; Plant cell(Telophase): © Jack M. Bostrack/Visuals Unlimited;

M

IT

O

S

(34)

Phases of Mitosis in Animal

and Plant Cells

• Functions of mitosis:



Permits growth and repair.



In flowering plants, meristematic tissue

retains the ability to divide throughout the

life of the plant



In mammals, mitosis is necessary when:

• A fertilized egg becomes an embryo

• An embryo becomes a fetus

(35)

Phases of Mitosis in Animal

and Plant Cells

• Stem Cells



Many mammalian organs contain stem cells

• Retain the ability to divide

• Red bone marrow stem cells divide to produce various

types of blood cells



Therapeutic cloning

to produce human tissues

can begin with either adult stem cells or embryonic

stem cells



Embryonic stem cells can be used for

reproductive

(36)

Reproductive and Therapeutic

Cloning

remove and

discard egg

nucleus

egg

remove

G

o

nucleus

G

o

cells from

animal to be

cloned

egg

fuse egg

with G

o

nucleus

Implant

embryo

into

surrogate

mother

Clone is born

culture

embryonic

stem cells

nervous

blood

muscle

embryonic

stem cells

culture

fuse egg

with G

o

nucleus

remove and

discard egg

nucleus

G

o

somatic cells

remove

G

o

nucleus

(37)

9.3 The Cell Cycle and Cancer

• Abnormal growth of cells is called a

tumor



Benign

tumors are not cancerous

• Encapsulated

• Do not invade neighboring tissue or spread



Malignant

tumors are cancerous

• Not encapsulated

• Readily invade neighboring tissues

• May also detach and lodge in distant places (metastasis)

• Results from mutation of genes regulating the cell cycle

• Development of

cancer



Tends to be gradual

(38)

The Cell Cycle and Cancer

• Characteristics of Cancer Cells



Lack differentiation

• Are non-specialized

• Are immortal (can enter cell cycle repeatedly)



Have abnormal nuclei

• May be enlarged

• May have abnormal number of chromosomes

• Often have extra copies of genes



Do not undergo apoptosis

• Normally, cells with damaged DNA undergo apoptosis

• The immune system can also recognize abnormal cells and

trigger apoptosis

(39)

The Cell Cycle and Cancer

• Characteristics of Cancer Cells



Form tumors

• Mitosis is normally controlled by contact with

neighboring cells – contact inhibition

• Cancer cells have lost contact inhibition



Undergo metastasis

• Original tumor easily fragments

• New tumors appear in other organs



Undergo

angiogenesis

• Formation of new blood vessels

(40)

Progression of Cancer

primary tumor

New mutations arise, and one cell (brown) has the ability to start a tumor.

Cancer in situ. The tumor is at its place of origin. One cell (purple)

mutates further.

Cancer cells now have the ability to invade lymphatic and blood vessels

and travel throughout the body.

lymphatic

vessel

blood

vessel

lymphatic

vessel

(41)

(42)

The Cell Cycle and Cancer

• Origin of Cancer



Oncogenes

• Proto-oncogenes

promote the cell cycle in

various ways

• If a proto-oncogene is mutated, it may become an

oncogene



Tumor suppressor genes

inhibit the cell

cycle in various ways

• If a tumor suppressor gene becomes inactive, it

may promote cancer development



Both proto-oncogenes and tumor suppressor

(43)

The Cell Cycle and Cancer

• Origin of Cancer



Chromosomes normally have special material

at each end called

telomeres



These get shorter each cell division



When they get very short, the cell will no

longer divide



Telomerase is an enzyme that maintains the

length of telomeres



Mutations in telomerase gene:

(44)

Causes of

Cancer

activated signaling protein growth factor receptor protein signaling protein phosphate

b. Effect of growth factor

P

P P

proto-oncogene

Codes for a growth factor,

a receptor protein, or a

signaling protein in a

stimulatory pathway.

If a proto-oncogene

becomes an oncogene,

the end result can be

active cell division.

tumor suppressor gene

Codes for a signaling

protein in an inhibitory

pathway. If a tumor

suppressor gene mutates,

the end result can be

active cell division.

c. Stimulatory pathway and

inhibitory pathway

1,100X

d. Cancerous skin cell

gene product

promotes

cell cycle

Stimulatory

pathway

Inhibitory

pathway

gene product

inhibits

cell cycle

growth factor

Activates signaling

proteins in a stimulatory

pathway that extends

to the nucleus.

a. Influences that cause mutated proto-oncogenes

(called oncogenes) and mutated tumor

suppressor genes

(45)

9.4 Prokaryotic Cell Division

• The prokaryotic chromosome is a ring of DNA



Folded up in an area called the

nucleoid



1,000 X the length of cell



Replicated into two rings prior to cell division



Replicated rings attach to the plasma membrane

• Binary fission



Splitting in two



Two replicate chromosomes are distributed to two

daughter cells



Produces two daughter cells identical to original cell –

(46)

Binary Fission

chromosome

cell wall

plasma

membrane

cytoplasm

1. Attachment of chromosome to

(47)

Binary Fission

chromosome

cell wall

plasma

membrane

cytoplasm

1. Attachment of chromosome to

a special plasma membrane

site indicates that this

bacterium is about to divide.

(48)

Binary Fission

chromosome

cell wall

plasma

membrane

cytoplasm

1. Attachment of chromosome to

a special plasma membrane

site indicates that this

bacterium is about to divide.

2. The cell is preparing for binary

fission by enlarging its cell wall,

plasma membrane, and overall

volume.

(49)

Binary Fission

chromosome

cell wall

plasma

membrane

cytoplasm

1. Attachment of chromosome to

a special plasma membrane

site indicates that this

bacterium is about to divide.

2. The cell is preparing for binary

fission by enlarging its cell wall,

plasma membrane, and overall

volume.

3. DNA replication has produced

two identical chromosomes.

Cell wall and plasma membrane

begin to grow inward.

(50)

Binary Fission