Download Chapter 19

Fig. 19-1
0.5 µm
Fig. 19-2
RESULTS
1 Extracted sap 2 Passed sap
from tobacco
plant with
tobacco
mosaic
disease
3 Rubbed filtered
through a
porcelain
filter known
to trap
bacteria
4 Healthy plants
became infected
sap on healthy
tobacco plants
Fig. 19-3
RNA
DNA
Capsomere
Membranous
envelope
RNA
Head
DNA
Capsid
Tail
sheath
Capsomere
of capsid
Glycoproteins
Glycoprotein
18  250 nm
70–90 nm (diameter) 80–200 nm (diameter)
20 nm
50 nm
(a) Tobacco mosaic (b) Adenoviruses
virus
50 nm
Tail
fiber
80  225 nm
50 nm
(c) Influenza viruses (d) Bacteriophage T4
Fig. 19-3a
RNA
Capsomere
of capsid
18  250 nm
20 nm
(a) Tobacco mosaic
virus
Fig. 19-3b
DNA
Capsomere
Glycoprotein
70–90 nm (diameter)
50 nm
(b) Adenoviruses
Fig. 19-3c
Membranous
envelope
RNA
Capsid
Glycoproteins
80–200 nm (diameter)
50 nm
(c) Influenza viruses
Fig. 19-3d
Head
DNA
Tail
sheath
Tail
fiber
80  225 nm
50 nm
(d) Bacteriophage T4
Fig. 19-4
VIRUS
1 Entry and
DNA
uncoating
Capsid
3 Transcription
and manufacture
of capsid proteins
2 Replication
HOST CELL
Viral DNA
mRNA
Viral DNA
Capsid
proteins
4 Self-assembly of
new virus particles
and their exit from
the cell
Fig. 19-5-1
1 Attachment
Fig. 19-5-2
1 Attachment
2 Entry of phage
DNA and
degradation of
host DNA
Fig. 19-5-3
1 Attachment
2 Entry of phage
DNA and
degradation of
host DNA
3 Synthesis of viral
genomes and
proteins
Fig. 19-5-4
1 Attachment
2 Entry of phage
DNA and
degradation of
host DNA
Phage assembly
4 Assembly
3 Synthesis of viral
genomes and
proteins
Head
Tail Tail fibers
Fig. 19-5-5
1 Attachment
2 Entry of phage
5 Release
DNA and
degradation of
host DNA
Phage assembly
4 Assembly
3 Synthesis of viral
genomes and
proteins
Head
Tail Tail fibers
Fig. 19-6
Phage
DNA
Daughter cell
with prophage
The phage injects its DNA.
Cell divisions
produce
population of
bacteria infected
with the prophage.
Phage DNA
circularizes.
Phage
Bacterial
chromosome
Occasionally, a prophage
exits the bacterial
chromosome,
initiating a lytic cycle.
Lytic cycle
Lysogenic cycle
The bacterium reproduces,
copying the prophage and
transmitting it to daughter cells.
The cell lyses, releasing phages.
Lytic cycle
is induced
or
New phage DNA and proteins
are synthesized and
assembled into phages.
Lysogenic cycle
is entered
Prophage
Phage DNA integrates into
the bacterial chromosome,
becoming a prophage.
Table 19-1
Table 19-1a
Table 19-1b
Fig. 19-7
Capsid and viral genome
enter the cell
Capsid
RNA
HOST CELL
Envelope (with
glycoproteins)
Viral genome (RNA)
Template
mRNA
Capsid
proteins
ER
Glycoproteins
Copy of
genome (RNA)
New virus
Fig. 19-8
Glycoprotein
Viral envelope
Capsid
Reverse
transcriptase
HIV
RNA (two
identical
strands)
HIV
Membrane of
white blood cell
HOST CELL
Reverse
transcriptase
Viral RNA
RNA-DNA
hybrid
0.25 µm
DNA
HIV entering a cell
NUCLEUS
Provirus
Chromosomal
DNA
RNA genome
for the
next viral
generation
New virus
New HIV leaving a cell
mRNA
Fig. 19-8a
Glycoprotein
Viral envelope
Capsid
Reverse
transcriptase
RNA (two
identical
strands)
HOST CELL
HIV
Reverse
transcriptase
Viral RNA
RNA-DNA
hybrid
DNA
NUCLEUS
Provirus
Chromosomal
DNA
RNA genome
for the
next viral
generation
New virus
mRNA
Fig. 19-8b
HIV
Membrane of
white blood cell
0.25 µm
HIV entering a cell
New HIV leaving a cell
Fig. 19-9
(a) The 1918 flu pandemic
0.5 µm
(b) Influenza A
H5N1 virus
(c) Vaccinating ducks
Fig. 19-9a
(a) The 1918 flu pandemic
Fig. 19-9b
0.5 µm
(b) Influenza A H5N1
virus
Fig. 19-9c
(c) Vaccinating ducks
Fig. 19-10
Fig. 19-10a
Fig. 19-10b
Fig. 19-10c
Fig. 19-11
Prion
Normal
protein
Original
prion
New
prion
Aggregates
of prions
Fig. 19-UN1
Phage
DNA
The phage attaches to a
host cell and injects its DNA
Bacterial
chromosome
Lytic cycle
• Virulent or temperate phage
• Destruction of host DNA
• Production of new phages
• Lysis of host cell causes release
of progeny phages
Prophage
Lysogenic cycle
• Temperate phage only
• Genome integrates into bacterial
chromosome as prophage, which
(1) is replicated and passed on to
daughter cells and
(2) can be induced to leave the
chromosome and initiate a lytic cycle
Number of bacteria
A
Time
Number of viruses
Fig. 19-UN2
B
Time
Fig. 19-UN3