1. Fig. 19-1
Figure 19.1 Are the tiny viruses infecting this E. coli cell alive?
0.5 µm

2. RESULTS Extracted sap from tobacco plant with tobacco mosaic disease
Fig. 19-2
RESULTS 1
Extracted sap
from tobacco
plant with
tobacco
mosaic
disease 2
Passed sap
through a
porcelain
filter known
to trap
bacteria 3
Rubbed filtered
sap on healthy
tobacco plants
Figure 19.2 What causes tobacco mosaic disease? 4
Healthy plants
became infected

3. RNA DNA Membranous envelope Head RNA Capsomere DNA Capsid Tail sheath
Fig. 19-3
RNA
DNA
Membranous
envelope
Head
RNA
Capsomere
DNA
Capsid
Tail
sheath
Capsomere
of capsid
Tail
fiber
Glycoprotein
Glycoproteins
18  250 nm
70–90 nm (diameter)
80–200 nm (diameter)
80  225 nm
Figure 19.3 Viral structure
20 nm
50 nm
50 nm
50 nm
(a) Tobacco mosaic
virus
(b) Adenoviruses
(c) Influenza viruses
(d) Bacteriophage T4

4. 18  250 nm RNA Capsomere of capsid (a) Tobacco mosaic virus 20 nm
Fig. 19-3a
RNA
Capsomere
of capsid
18  250 nm
Figure 19.3 Viral structure
20 nm
(a) Tobacco mosaic
virus

5. DNA Capsomere Glycoprotein 70–90 nm (diameter) (b) Adenoviruses 50 nm
Fig. 19-3b
DNA
Capsomere
Glycoprotein
70–90 nm (diameter)
Figure 19.3 Viral structure
50 nm
(b) Adenoviruses

6. Membranous envelope RNA Capsid Glycoproteins 80–200 nm (diameter)
Fig. 19-3c
Membranous
envelope
RNA
Capsid
Glycoproteins
80–200 nm (diameter)
Figure 19.3 Viral structure
50 nm
(c) Influenza viruses

7. Head DNA Tail sheath Tail fiber 80  225 nm (d) Bacteriophage T4 50 nm
Fig. 19-3d
Head
DNA
Tail
sheath
Tail
fiber
80  225 nm
Figure 19.3 Viral structure
50 nm
(d) Bacteriophage T4

8. VIRUS Entry and uncoating DNA Capsid Transcription and manufacture
Fig. 19-4
VIRUS
Entry and
uncoating 1
DNA
Capsid
Transcription
and manufacture
of capsid proteins 3 2
Replication
HOST CELL
Viral DNA
mRNA
Viral DNA
Capsid
proteins
Figure 19.4 A simplified viral reproductive cycle
Self-assembly of
new virus particles
and their exit from
the cell 4

9. Fig 1
Attachment
Figure 19.5 The lytic cycle of phage T4, a virulent phage

10. Attachment Entry of phage DNA and degradation of host DNA 1 2
Fig 1
Attachment 2
Entry of phage
DNA and
degradation of
host DNA
Figure 19.5 The lytic cycle of phage T4, a virulent phage

11. Attachment Entry of phage DNA and degradation of host DNA
Fig 1
Attachment 2
Entry of phage
DNA and
degradation of
host DNA
Figure 19.5 The lytic cycle of phage T4, a virulent phage 3
Synthesis of viral
genomes and
proteins

12. Attachment Entry of phage DNA and degradation of host DNA
Fig 1
Attachment 2
Entry of phage
DNA and
degradation of
host DNA
Phage assembly
Figure 19.5 The lytic cycle of phage T4, a virulent phage 4
Assembly 3
Synthesis of viral
genomes and
proteins
Head
Tail
Tail fibers

13. Attachment Entry of phage DNA and degradation of host DNA Release
Fig 1
Attachment 2
Entry of phage
DNA and
degradation of
host DNA 5
Release
Phage assembly
Figure 19.5 The lytic cycle of phage T4, a virulent phage 4
Assembly 3
Synthesis of viral
genomes and
proteins
Head
Tail
Tail fibers

14. The phage injects its DNA.
Fig. 19-6
Daughter cell
with prophage
Phage
DNA
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
Lysogenic cycle
is entered
Figure 19.6 The lytic and lysogenic cycles of phage λ, a temperate phage
Prophage
New phage DNA and proteins
are synthesized and
assembled into phages.
Phage DNA integrates into
the bacterial chromosome,
becoming a prophage.

15. Table 19-1
Table 1

16. Table 19-1a
Table 1

17. Table 19-1b
Table 1

18. Capsid and viral genome enter the cell Capsid
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
Copy of
genome (RNA)
Glyco-
proteins
Figure 19.7 The reproductive cycle of an enveloped RNA virus
New virus

19. Fig. 19-8
Glycoprotein
Viral envelope
Capsid
RNA (two
identical
strands)
Reverse
transcriptase
HIV
Membrane of
white blood cell
HIV
HOST CELL
Reverse
transcriptase
Viral RNA
RNA-DNA
hybrid
0.25 µm
HIV entering a cell
DNA
NUCLEUS
Provirus
Chromosomal
DNA
Figure 19.8 The reproductive cycle of HIV, the retrovirus that causes AIDS
RNA genome
for the
next viral
generation
mRNA
New virus
New HIV leaving a cell

20. Viral envelope Glycoprotein Capsid RNA (two identical strands) Reverse
Fig. 19-8a
Glycoprotein
Viral envelope
Capsid
RNA (two
identical
strands)
Reverse
transcriptase
HOST CELL
HIV
Reverse
transcriptase
Viral RNA
RNA-DNA
hybrid
DNA
NUCLEUS
Provirus
Chromosomal
DNA
RNA genome
for the
next viral
generation
Figure 19.8 The reproductive cycle of HIV, the retrovirus that causes AIDS
mRNA
New virus

21. Membrane of white blood cell HIV HIV entering a cell
Fig. 19-8b
Membrane of
white blood cell
HIV
Figure 19.8 The reproductive cycle of HIV, the retrovirus that causes AIDS
0.25 µm
HIV entering a cell
New HIV leaving a cell

22. (a) The 1918 flu pandemic (b) Influenza A H5N1 virus
Fig. 19-9
(a) The 1918 flu pandemic
0.5 µm
Figure 19.9 Influenza in humans and other animals
For the Discovery Video Emerging Diseases, go to Animation and Video Files.
(b) Influenza A
H5N1 virus
(c) Vaccinating ducks

23. (a) The 1918 flu pandemic Fig. 19-9a
Figure 19.9 Influenza in humans and other animals
(a) The 1918 flu pandemic

24. (b) Influenza A H5N1 virus 0.5 µm Fig. 19-9b
Figure 19.9 Influenza in humans and other animals
(b) Influenza A H5N1
virus

25. (c) Vaccinating ducks Fig. 19-9c
Figure 19.9 Influenza in humans and other animals
(c) Vaccinating ducks

26. Fig
Figure Viral infection of plants

27. Fig a
Figure Viral infection of plants

28. Fig b
Figure Viral infection of plants

29. Fig c
Figure Viral infection of plants

30. Original Prion prion Aggregates of prions New prion Normal protein
Fig
Original
prion
Prion
Aggregates
of prions
New
prion
Normal
protein
Figure Model for how prions propagate

31. host cell and injects its DNA Phage DNA
Fig. 19-UN1
The phage attaches to a
host cell and injects its DNA
Phage
DNA
Bacterial
chromosome
Prophage
Lytic cycle
Lysogenic cycle
Virulent or temperate phage
Destruction of host DNA
Production of new phages
Lysis of host cell causes release
of progeny phages
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

32. Fig. 19-UN2 A B
Number of bacteria
Number of viruses
Time
Time

33. Fig. 19-UN3

34. You should now be able to:
Explain how capsids and envelopes are formed
Distinguish between the lytic and lysogenic reproductive cycles
Explain why viruses are obligate intracellular parasites
Describe the reproductive cycle of an HIV retrovirus
Describe three processes that lead to the emergence of new diseases
Describe viroids and prions