Download 5a Cell Division

Cell Division and Gene Expression
• The Need for Cell Reproduction
- The Nature of Chromosomes
- The Cell Cycle
- Mitosis and Cytokinesis
- Cancer Cells: Abnormal Cell Cycle
• The Expression of Genes as Proteins: DNA gene --> RNA --> Protein
- Transcription by RNA Polymerase
- The Three Types of RNA
- Translation by Ribosome
What Cell Reproduction Accomplishes
• Reproduction
– The birth of new organisms.
– Occurs much more often at the cellular level
• Cell division plays a role in
– The replacement of lost or damaged cells.
– Cell reproduction and growth.
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Passing On Genes from Cell to Cell
• Before a parent cell divides, it duplicates its
chromosomes.
• The two resulting “daughter” cells are genetically
identical, each getting a duplicate set of
chromosomes
Cell Division and Gene Expression
• The Need for Cell Reproduction
- Copying Chromosomes
- The Cell Cycle
- Mitosis and Cytokinesis
- Cancer Cells: Abnormal Cell Cycle
• The Expression of Genes as Proteins: DNA gene --> RNA --> Protein
- Transcription by RNA Polymerase
- The Three Types of RNA
- Translation by Ribosome
Types of Reproduction
•
Asexual reproduction
•
–
Single cells reproduce by mitosis
–
Two daughter cells produced from one parent cell
•
Daughter cells are genetically identical to each other
•
Daughter cells are genetically identical to the parent cell
–
Use for growth and repair as well as producing new individuals
–
Finding a mate is unnecessary
–
Relatively “cheap” energetically
Sexual reproduction
–
Single or multi-celled organisms reproduce by meiosis
–
Four daughter cells called gametes (eggs and sperm) produced from one parent cell
•
Gametes are genetically different from each other and parent cell
•
Gametes must unite with other gametes of opposite type to produce viable organism
–
Used solely for making more individual single or multicellular organisms
–
A mate or a second organ for producing other gametes is required
–
Relatively “expensive” energetically; lower efficiency in producing offspring
Both Daughter Cells in Mitosis Must Get Chromosomes
12
chromosomes
Duplication (Replication)
12 + 12
chromosomes
?
12
12
chromosomes
chromosomes
DNA Replication (Duplication) Occurs in S Phase of the Cell Cycle
DNA Replication is Performed by DNA Polymerase
Chromosome
Free nucleotides
DNA polymerase
Old strand acts as a
template for synthesis
of new strand
Leading strand
Old DNA
Helicase unwinds
the double helix and
exposes the bases
Replication
fork
Adenine
Thymine
Cytosine
Guanine
Two new strands (leading and lagging)
synthesized in opposite directions
Lagging
strand
DNA polymerase Old (template) strand
Figure 3.32
Cell Division and Gene Expression
• The Need for Cell Reproduction
- The Nature of Chromosomes
- The Cell Cycle
- Mitosis and Cytokinesis
- Cancer Cells: Abnormal Cell Cycle
• The Expression of Genes as Proteins: DNA gene --> RNA --> Protein
- Transcription by RNA Polymerase
- The Three Types of RNA
- Translation by Ribosome
The Cell Cycle
G1 checkpoint
(restriction point)
S
Growth and DNA
synthesis
G1
Growth
M
G2
Growth and final
preparations for
division
G2 checkpoint
>95% of the cells in your body
are not progressing through the
cell cycle and will never divide
Chromosomes Must Be Condensed or Packaged Before Cell Division
DNA Packing
Cell Division and Gene Expression
• The Need for Cell Reproduction
- The Nature of Chromosomes
- The Cell Cycle
- Mitosis and Cytokinesis
- Cancer Cells: Abnormal Cell Cycle
• The Expression of Genes as Proteins: DNA gene --> RNA --> Protein
- Transcription by RNA Polymerase
- The Three Types of RNA
- Translation by Ribosome
Mitosis Overview
Prophase
Metaphase
Anaphase
Telophase/
Cytokinesis
Mitosis (All Phases)
Animal Mitosis
Sea Urchin (time lapse)
G2 of Interphase:
To M Phase:
• Chromosomes
indistinct
1.
Prophase
• Centrosomes
replicate
2.
Metaphase
3.
Anaphase
4.
Telophase and
Cytokinesis
Late Interphase
Mitosis Overview
Figure 8.8.1
Prophase
Prometaphase
Metaphase
1. Chromosomes
1. Chromosomes condense, become visible
line up in a column
2. Nuclear membrane dissolves
90o to spindle
3. Centrioles move to opposite poles, grow fibers
Figure 8.8.2
Anaphase
1. Sister chromatids
separate and move
towards opposite poles
Telophase
1. Chromosomes unwind (decondense)
2. Two nuclear membranes reform
3. Cell divides in half (cytokinesis)
Cell Splitting in Telophase: Cytokinesis
•
Cytokinesis
–
Typically occurs during telophase.
–
Involves contracting microfilaments
Cytokinesis
Mitosis Overview
Prophase
Metaphase
Anaphase
Telophase/
Cytokinesis
Mitosis (All Phases)
Animal Mitosis
Sea Urchin (time lapse)
Cell Division and Gene Expression
• The Need for Cell Reproduction
- The Nature of Chromosomes
- The Cell Cycle
- Mitosis and Cytokinesis
- Cancer Cells: Abnormal Cell Cycle
• The Expression of Genes as Proteins: DNA gene --> RNA --> Protein
- Transcription by RNA Polymerase
- The Three Types of RNA
- Translation by Ribosome
Cancer Cells: Growing Out of Control
• Normal plant and animal cells have a cell cycle
control system.
• Cancer is a disease of the cell cycle.
• Cancer cells do not respond normally to the cell
cycle control system.
• Cancer cells can form tumors,
– Abnormally growing masses of body cells.
• If a tumor is malignant and metastasizes it can
spread to other parts of the body.
Breast Cancer
Figure 8.10
Cell Division and Gene Expression
• The Need for Cell Reproduction
- The Nature of Chromosomes
- The Cell Cycle
- Mitosis and Cytokinesis
- Cancer Cells: Abnormal Cell Cycle
• The Expression of Genes as Proteins: DNA gene --> RNA --> Protein
- Transcription by RNA Polymerase
- The Three Types of RNA
- Translation by Ribosome
Central Dogma of Biology: How Shape and Form Are Dictated By DNA Genes
Genotype:
The genes
carried in a
cell for a
particular
trait
Phenotype:
The physical
expression of
genes for a
particular trait
A segment of
DNA (gene)
carries
specific coded
instructions
for the making
of a single
proteins.
Nuclear
envelope
Transcription
RNA Processing
DNA
Pre-mRNA
mRNA
Translation
Nuclear
pores
Ribosome
Polypeptide
Figure 3.34