Transcript VIRUSES

BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 10
Molecular Biology of the Gene
Virus Structure, Replication and
the Body’s Defense
Modules 10.17, 24.1-6
From PowerPoint® Lectures for Biology: Concepts & Connections
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VIRUSES: GENES IN PACKAGES
10.17 Viral DNA may become part of the host
chromosome
Phage
Attaches
to cell
Bacterial
chromosome
Phage DNA
Cell lyses,
releasing phages
Phage injects DNA
Many cell
divisions
Occasionally a prophage
may leave the bacterial
chromosome
LYTIC CYCLE
Phages
assemble
LYSOGENIC CYCLE
Phage DNA
circularizes
Prophage
Lysogenic bacterium
reproduces normally,
replicating the prophage
at each cell division
OR
New phage DNA and
proteins are synthesized
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Phage DNA inserts into the bacterial
chromosome by recombination
Click on Video links to Understand How Virus
Replicate…….
• Lambda Phage Viral Replication (test)
• Replication of a Retrovirus (enrichment)
• HIV Replication (enrichment)
• HIV Replication Animation (enrichment)
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10.18 Connection: Many viruses cause disease in
animals
• Many viruses
have RNA,
rather than
DNA, as their
genetic material
Membranous
envelope
RNA
– Example: flu
viruses
Protein
coat
Glycoprotein spike
Figure 10.18A
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Glycoprotein spike
VIRUS
This slide is
enrichment
material
• Some animal
viruses steal a bit
of the host cell’s
membrane
Protein coat
Viral RNA
(genome)
Plasma
membrane
of host
cell
Envelope
1
Entry
2
Uncoating
3
RNA synthesis
by viral enzyme
Viral RNA
(genome)
4
Protein
synthesis
5 RNA synthesis
(other strand)
Template
mRNA
New
viral proteins
protein
6
New viral
genome
Assembly
Exit
7
Figure 10.18B
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10.19 Connection: Plant viruses are serious
agricultural pests
• Most plant viruses have RNA
– Example: tobacco mosaic disease
Protein
Figure 10.19
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RNA
10.20 Connection: Emerging viruses threaten
human health
• The deadly Ebola virus
causes hemorrhagic
fever
– Each virus is an
enveloped thread of
protein-coated RNA
• Hantavirus is another
enveloped RNA virus
Figure 10.20A, B
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10.21 The AIDS virus makes DNA on an RNA
template
• HIV is a retrovirus: This is a good diagram to
model virus parts
Envelope
Glycoprotein
Protein
coat
RNA
(two identical
strands)
Reverse
transcriptase
Figure 10.21A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
This is optional information if you are interested in retrovirus
replication. You have knowledge to understand it.
• Inside a cell,
HIV uses its
RNA as a
template for
making DNA
to insert into
the host
chromosome
Viral RNA
CYTOPLASM
1
NUCLEUS
DNA
strand
Chromosomal
DNA
2
3
Doublestranded
DNA
Provirus
DNA
4
5
RNA
Viral
RNA
and
proteins
6
Figure 10.21B
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10.22 Virus research and molecular genetics are
intertwined
• Virus studies help
establish molecular
genetics
• Molecular genetics helps
us understand viruses
– such as HIV, seen here
attacking a white blood
cell
Figure 10.22
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NONSPECIFIC DEFENSES AGAINST
INFECTION
24.1 Nonspecific defenses against infection include
the skin and mucous membranes, phagocytic
cells, and antimicrobial proteins
• The body’s first lines of defense against
infection are nonspecific
– They do not distinguish one infectious microbe
from another
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• Macrophages wander in the interstitial fluid
– They “eat” any bacteria and virus-infected
cells they encounter
Figure 24.1A
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• Interferon and complement proteins are
activated by infected cells
Viral nucleic acid
VIRUS
6 Antiviral proteins block
1
viral reproduction
2 Interferon
New viruses
genes
turned on
mRNA
5 Interferon
3
stimulates
cell to turn
on genes
for antiviral
proteins
Interferon
molecules
HOST CELL 1
Makes interferon;
is killed by virus
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4
HOST CELL 2
Protected against virus
by interferon from cell 1
Figure 24.1B
24.2 The inflammatory response mobilizes
nonspecific defense forces
• Tissue damage triggers the inflammatory
response
Skin surface
Swelling
Pin
Phagocytes
Bacteria
Phagocytes and
fluid move
into area
Chemical
signals
White
blood cell
1 Tissue injury; release of
chemical signals such as
histamine
2 Dilation and increased leakiness
3 Phagocytes (macrophages and
of local blood vessels; migration
of phagocytes to the area
neutrophils) consume bacteria
and cell debris; tissue heals
Figure 24.2
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How Does the Body Defend Against Pathogens?
Two Types of Defense Mechanisms:
1. Nonspecific Defense
2. Specific Defense
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• The inflammatory response can
– disinfect tissues
– limit further infection
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24.10 Antibodies are the weapons of humoral
immunity
• An antibody molecule
Figure 24.10A
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• An antibody molecule has antigen-binding sites
specific to the antigenic determinants that
elicited its secretion
Antigen-binding
sites
Light
chain
Heavy
chain
Figure 24.10B
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24.11 Antibodies mark antigens for elimination
• Antibodies may
– block harmful antigens on microbes
– clump bacteria or viruses together
– precipitate dissolved antigens
– activate complement proteins
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Binding of antibodies to antigens
inactivates antigens by
Neutralization
(blocks viral binding sites;
coats bacterial toxins)
Agglutination
of microbes
Precipitation of
dissolved antigens
Complement
molecule
Bacteria
Virus
Antigen
molecules
Bacterium
Enhances
Phagocytosis
Activation
of complement
Foreign cell
Hole
Leads to
Cell lysis
Macrophage
Figure 24.11
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Lab: “What Happens When Holly Gets Sick?”
• Holly Gets Sick Movie
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Click on the links to understand how the body
fights pathogens: Good but may be a bit
confusing. Study the Holly Gets Sick Video
Questions
• The Immune Response
• Cytotoxic T Cell and the Target Cell
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