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PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 12

The Cell Cycle

Key Roles of Cell Division

Unicellular organisms

Reproduce by cell division

100 µm

Figure 12.2 A

Key Roles of Cell Division

Multicellular organisms

Development from a fertilized cell

Growth

Repair

20 µm

200 µm

(b) Growth and development.

Figure 12.2 B, C

Concept 12.1

How does Cell division results in genetically identical daughter cells?

Concept 12.1

How does Cell division results in genetically identical daughter cells?

Cells duplicate their genetic material before they divide

A cell’s DNA = Genome

Genome

Chromosomes

DNA molecule and proteins (Chromatin)

Genes

50 µm

Cell not dividing =

Chromosomes thin, loosely packed
fibers called chromatin

Cell not dividing =

Chromosomes thin, loosely packed
fibers called chromatin

Cell dividing =

Individual Chromosomes visible

Before a cell divides chromosomes replicate

= sister chromatids joined
together at the
centromere

Figure 8.4B

Before a cell divides chromosomes replicate

= sister chromatids joined
together at the
centromere

Figure 8.4B

Before a cell divides chromosomes replicate

= sister chromatids joined
together at the
centromere

Figure 8.4B

During Cell division sister chromatids separate

2 daughter cells
each contain
a complete,
identical set of
chromosomes

Figure 8.4C

The cell cycle

2 major phases- Interphase and Mitotic

Figure 8.5

Interphase- 3 subphases

G1 phase

S phase

G2 phase

Figure 8.5

Interphase

Cell parts are made (G1, G2 phase)

Chromosomes duplicate (S phase)

Mitotic phase

Duplicated chromosomes separate

Separated chromosomes are distributed into two daughter cells

What Happens During Each Phase?

Interphase + Mitotic Phase = Cell cycle:

Interphase

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

The 5 stages of cell division

Figure 8.6 (Part 1)

Interphase:

- Cell growth

Chromosomes condense
Chromosomes duplicate
Nuclear envelope begins to breakdown

The stages of cell division

Figure 8.6 (Part 1)

Prophase:

Duplicated Chromosomes appear as 2 sister chromatids connected at the centromere

- Mitotic spindle forms in cytoplasm from centrosomes

The stages of cell division

Figure 8.6 (Part 1)

Metaphase:

Mitotic spindle fully formed

Duplicated Chromosomes line up on metaphase plate located in middle of the cell

Each sister chromatid is attached to a spindle fiber

The stages of cell division

Figure 8.6 (Part 1)

Anaphase:

Sister chromatids are pulled apart and taken to opposite poles of the cell by the spindle fibers

Cell elongates

The stages of cell division

Telophase:

Roughly opposite prophase:

Nuclear envelopes begin to reform around chromosomes

Chromosomes begin to uncoil

Mitotic spindle disappears

Mitosis complete!

The stages of cell division

Cytokinesis:

-Division of the cytoplasm

-Animals = cleavage furrow

Cytokinesis differs for plant and animal cells

Animals

Cytokinesis occurs
by a constriction of
the cell (cleavage)

Figure 8.7A

Plants

membranous cell
plate (golgi vesicles) forms and splits the cell in two

Figure 8.7B

What Phase of Mitosis?

8.11 Review: stages of mitosis

Figure 8.11A

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. Those cells would have __________ picograms at the end of the S phase and __________ picograms at the end of G2.

A 8 ... 8

B 8 ... 16

C 16 ... 8

D 16 ... 16

E 12 ... 16

Answer: d

Source: Barstow - Test Bank for Biology, Sixth Edition, Question #50

The Mitotic Spindle: A Closer Look

The mitotic spindle

Is an apparatus of microtubules that controls chromosome movement during mitosis

The Spindle

Centrosomes
Spindle microtubules
Asters

How are chromosomes pulled to poles?

Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis, what would be the result?

A a cell with a single large nucleus

B a cell with high concentrations of actin
and myosin

C a cell with two abnormally small nuclei

D a cell with two nuclei

E a cell with two nuclei but with half the
amount of DNA

Answer: d

Source: Barstow - Test Bank for Biology, Sixth Edition, Question #20

Binary Fission: Prokaryotes (bacteria)

Origin of replication = duplicated

Binary Fission Prokaryotes (bacteria)

Origin of replication = duplicated

One copy of origin moves to opposite end

Binary Fission Prokaryotes (bacteria)

Origin of replication = duplicated

One copy of origin moves to opposite end

Replication continues; cell elongates

Review

Interphase + Mitotic phase = Cell division in Eukaryotes
Binary Fission- Cell division in Prokaryotes

Similarities and Differences?

Mitotic Spindle- How do sisters move to poles?

How are chromosomes pulled to poles?

Concept 12.3 How is cell cycle is regulated ?

= Molecular control system

- Controls frequency of cell division

- Ex: Skin vs. muscle cells

The Cell Cycle Control System

3 checkpoints of the cell cycle

The Cell Cycle Control System

3 checkpoints of the cell cycle

Cell cycle stops (G0) until a go-ahead signal is received

The Cell Cycle Control System

G2 Checkpoint

What are the “go-ahead” signal molecules?

2 types of regulatory proteins:

1. Cyclins

2. Cyclin-dependent kinases* (Cdks)

*activate/inactivate proteins by phosphorylation

What are the “go-ahead” signal molecules?

2 types of regulatory proteins:

1. Cyclins

2. Cyclin-dependent kinases* (Cdks)

*activate/inactivate proteins by phosphorylation

G2 checkpoint “go-ahead” molecule

The activity of cyclins and Cdks for G2 checkpoint

The activity of cyclins and Cdks

Internal and external signals

Cell cycle checkpoint is control by:

Internal signals – Ex: MPF

External signals – Ex: PDGF

External factors for cell cycle control

Growth factors- Stimulate cells to divide
PDGF – platelet-derived growth factor

Fibroblast cell

External factors for cell cycle control

Growth factors- Stimulate cells to divide
PDGF – platelet-derived growth factor

Fibroblast cell

PDGF required for Fibroblast cell division

External factors for cell cycle control

Growth factors- Stimulate cells to divide
PDGF – platelet-derived growth factor

Fibroblast cell

PDGF required for Fibroblast cell division

PDGF Experiment

PGDF Experiment Results

External factors for cell cycle control

1. Anchorage dependence

2. Density-dependent inhibition

Cancer cells

Exhibit neither density-dependent inhibition nor anchorage dependence

Loss of Cell Cycle Controls in Cancer Cells

Cancer cells

Do not respond normally to the body’s control mechanisms

Form tumors:

Benign, malignant, metastatic

Benign, Malignant and Metastatic tumors

Figure 12.19

malignant

malignant  metastatic

Benign

Tumor

Glandular

tissue

Cancer cell

Blood
vessel

Lymph
vessel

Metastatic
Tumor

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List differences between:
Mitosis (eukaryotic cells)
Binary Fission (prokaryotic cells)

Differences between mitosis in eukaryotic cells and binary fission in prokaryotic cells:
Nuclear envelope
Spindle
Several chromosomes vs. one

Review

Cell division- Reproduction (unicellular)
Cell division- Development, Growth, Repair
Genetic material duplicated and divides BEFORE cell divides. WHY?

Chromosome

Sister Chromatids

2 Chromosomes

Review

Interphase + Mitotic phase = Cell division in Eukaryotes
Binary Fission- Cell division in Prokaryotes

Similarities and Differences?

Mitotic Spindle- How do sisters move to poles?

Review!

Ch. 12:
Cell Cycle Control

Molecular signals

Internal

G2 = MPF (cyclin +CdK)

External

Cancer