6. Fig. 19-2
RESULTS
1 2 3Extracted sap
from tobacco
plant with
tobacco
mosaic
disease
Passed sap
through a
porcelain
filter known
to trap
bacteria
Rubbed filtered
sap on healthy
tobacco plants
4 Healthy plants
became infected
19. Transcription
and manufacture
of capsid proteins
Self-assembly of
new virus particles
and their exit from
the cell
Entry and
uncoating
Fig. 19-4
VIRUS1
2
3
DNA
Capsid
4
Replication
HOST CELL
Viral DNA
mRNA
Capsid
proteins
Viral DNA
26. Fig. 19-5-5
Phage assembly
Head Tail Tail fibers
Assembly
Release
Synthesis of viral
genomes and
proteins
Entry of phage
DNA and
degradation of
host DNA
Attachment1
2
4
5
3
29. Fig. 19-6
Phage
DNA
Phage
The phage injects its DNA.
Bacterial
chromosome
Phage DNA
circularizes.
Daughter cell
with prophage
Occasionally, a prophage
exits the bacterial
chromosome,
initiating a lytic cycle.
Cell divisions
produce
population of
bacteria infected
with the prophage.
The cell lyses, releasing phages.
Lytic cycle
Lytic cycle
is induced
or
Lysogenic cycle
is entered
Lysogenic cycle
Prophage
The bacterium reproduces,
copying the prophage and
transmitting it to daughter cells.
Phage DNA integrates into
the bacterial chromosome,
becoming a prophage.
New phage DNA and proteins
are synthesized and
assembled into phages.
38. Fig. 19-8
Glycoprotein Viral envelope
Capsid
RNA (two
identical
strands)Reverse
transcriptase HIV
HIV
Membrane of
white blood cell
HIV entering a cell
0.25 µm
Viral RNA
RNA-DNA
hybrid
HOST CELL
Reverse
transcriptase
DNA
NUCLEUS
Provirus
Chromosomal
DNA
RNA genome
for the
next viral
generation
mRNA
New virus
New HIV leaving a cell
39. Fig. 19-8a
Glycoprotein
Reverse
transcriptase HIV
RNA (two
identical
strands)
Capsid
Viral envelope
HOST CELL
Reverse
transcriptase
Viral RNA
RNA-DNA
hybrid
DNA
NUCLEUS
Provirus
Chromosomal
DNA
RNA genome
for the
next viral
generation
mRNA
New virus
62. Fig. 19-UN1
Phage
DNA
Bacterial
chromosome
The phage attaches to a
host cell and injects its DNA
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
Lytic cycle
• Virulent or temperate phage
• Destruction of host DNA
• Production of new phages
• Lysis of host cell causes release
of progeny phages