A eukaryotic cell has many more genes than a prokaryotic cell

1
The large, complex chromosomes of eukaryotes
duplicate with each cell division
THE EUKARYOTIC CELL CYCLE AND MITOSIS

• A eukaryotic cell has many more genes than a
  prokaryotic cell
• The genes are grouped into multiple chromosomes,
  found in the nucleus
• The chromosomes of this plant cell are stained
  dark purple

2

• Chromosomes contain a very long DNA molecule with
  thousands of genes

• Individual chromosomes are only visibleduring
  cell division
• They are packaged as chromatin

3

• Before a cell starts dividing, the chromosomes
  are duplicated

Sister chromatids

• This process produces sister chromatids

Centromere
Figure 8.4B
4

• When the cell divides, the sister chromatids
  separate

Chromosomeduplication

• Two daughter cells are produced
• Each has a complete and identical set of
  chromosomes

Sister chromatids
Centromere
Chromosomedistributiontodaughtercells
Figure 8.4C
5
The cell cycle multiplies cells

• The cell cycle consists of two major phases
• Interphase, where chromosomes duplicate and cell
  parts are made
• The mitotic phase, when cell division occurs

6
Cell division is a continuum of dynamic changes

• Eukaryotic cell division consists of two stages
• Mitosis
• Cytokinesis

7

• In mitosis, the duplicated chromosomes are
  distributed into two daughter nuclei

• After the chromosomes coil up, a mitotic spindle
  moves them to the middle of the cell

8
INTERPHASE
PROPHASE
Centrosomes(with centriole pairs)
Early mitoticspindle
Centrosome
Fragmentsof nuclearenvelope
Kinetochore
Chromatin
Centrosome
Spindlemicrotubules
Nucleolus
Nuclearenvelope
Plasmamembrane
Chromosome,consisting of twosister chromatids
9

• The sister chromatids then separate and move to
  opposite poles of the cell

• The process of cytokinesis divides the cell into
  two genetically identical cells

10
METAPHASE
TELOPHASE AND CYTOKINESIS
ANAPHASE
Cleavagefurrow
Nucleolusforming
Metaphaseplate
Nuclearenvelopeforming
Spindle
Daughterchromosomes
11
Cytokinesis differs for plant and animal cells

• In animals, cytokinesis occurs by cleavage
• This process pinches the cell apart

Cleavagefurrow
Cleavagefurrow
Contracting ring ofmicrofilaments
Daughter cells
12
Cell plateforming
Wall ofparent cell
Daughternucleus

• In plants, a membranous cell plate splits the
  cell in two

Cell wall
New cell wall
Vesicles containingcell wall material
Cell plate
Daughtercells
13
Anchorage, cell density, and chemical growth
factors affect cell division

• Most animal cells divide only when stimulated,
  and others not at all
• In laboratory cultures, most normal cells divide
  only when attached to a surface
• They are anchorage dependent

14

• Cells continue dividing until they touch one
  another

• This is called density-dependent inhibition

Cells anchor to dish surface and divide.
When cells have formed a complete single layer,
they stop dividing (density-dependent inhibition).
If some cells are scraped away, the remaining
cells divide to fill the dish with a single layer
and then stop (density-dependent inhibition).
15

• Growth factors are proteins secreted by cells
  that stimulate other cells to divide

After forming a single layer, cells have stopped
dividing.
Providing an additional supply of growth factors
stimulates further cell division.
16
Growth factors signal the cell cycle control
system

• Proteins within the cell control the cell cycle
• Signals affecting critical checkpoints determine
  whether the cell will go through a complete cycle
  and divide

G1 checkpoint
Controlsystem
M checkpoint
G2 checkpoint
17

• The binding of growth factors to specific
  receptors on the plasma membrane is usually
  necessary for cell division

Growth factor
Plasma membrane
Relayproteins
G1 checkpoint
Receptor protein
Signal transduction pathway
Cell cyclecontrolsystem
18
Connection Growing out of control, cancer cells
produce malignant tumors

• Cancer cells have abnormal cell cycles
• They divide excessively and can form abnormal
  masses called tumors
• Radiation and chemotherapy are effective as
  cancer treatments because they interfere with
  cell division

19

• Malignant tumors can invade other tissues and may
  kill the organism

Lymphvessels
Tumor
Glandulartissue
Metastasis
1
2
3
A tumor grows from a single cancer cell.
Cancer cells invade neighboring tissue.
Cancer cells spread through lymph and blood
vessels to other parts of the body.
20
Review of the functions of mitosis Growth, cell
replacement, and asexual reproduction

• When the cell cycle operates normally, mitotic
  cell division functions in

21

• Cell replacement (seen here in skin)
• Growth (seen here in an onion root)

Deadcells
Epidermis, the outer layer of the skin
Dividingcells
Dermis
22

• Asexual reproduction (seen here in a hydra)

23
Cell Division Review

• There are 4 phases
• M,S,G1, and G2

• M phase aka. Mitosis, is when the cell
  nucleus
• divides and cytokinesis takes place

• S phase the copying of chromosomes

• G1 phase this is when cells increase and size
  
• and make stuff

• G2 phase this is when organelles and
  molecules
• required for cell division are produced

24

• Interphase
• Actually has three phases, G1, S and G2

• Mitosis four phases make is up
• Prophase, metaphase, anaphase, and telophase

25

• Prophase
• 1st phase
• Chromosomes form, nuclear membrane breaks down,
  and a spindle forms

• Metaphase
• 2nd phase
• Chromosomes line up and each is connected to the
  spindle fiber

26

• Anaphase
• 3rd phase
• Chromosomes split apart into sister chromatids
  and move apart

• Telophase
• Chromosomes gather at opposite ends and two
  nuclear membranes begin to form

27

• Cytokinesis each daughter cell pinches off

• Interphase
• 4th stage
• Cell grows and makes its own DNA