Illustration of Prion Infection Mechanism

FIGURE 20–21 Prion Infection Mechanism Prions are misfolded PrP proteins. The build-up of prions in brain tissue can cause disease by damaging nerve cells.

d

MYSTERY CLUE

Face of a cow.

BSE virtually disappeared when the British government banned the practice of using ground-up cattle tissue in protein feed supplements. Could prions be the cause of BSE?

Prions In 1972, American scientist Stanley Prusiner became interested in scrapie, an infectious disease in sheep, the exact cause of which was unknown. At first, he suspected a viral cause, but experiments revealed clumps of tiny protein particles in the brains of infected sheep. Prusiner called these particles prions, short for “protein infectious particles.” Although prions were first discovered in sheep, many animals, including humans, can become infected with prions. Prions are formed when a protein known as PrP is improperly folded. Prions themselves can cause PrP proteins to misfold, producing even more prions. An accumulation of prions can damage nerve cells, as shown in Figure 20–21.

20.3 Assessment

Review Key Concepts

    1. Review Describe how bacteria cause disease.

    2. Relate Cause and Effect Are vaccines effective before or after infection? Explain.

    1. Review How do viruses cause disease?

    2. Compare and Contrast How does the treatment of viral diseases contrast with the treatment of bacterial diseases?

    1. Review Why are emerging diseases of particular concern?

    2. Explain Why are “superbugs” difficult to control?

    3. Propose a Solution What actions could your school take to help combat the evolution of “superbugs”? Explain how these actions could make an impact.

BUILD VOCABULARY

  1. Research the word origins for the term vaccine. Which word in which language does it come from and why?

End ofPage 592

Table of Contents

Miller & Levine Biology
About the Authors
Changing the World of Biology Education
Contents
Diversity of Life: A Visual Guide DOL•1–DOL•64
Labs and Activities
Features
UNIT 1 The Nature of Life
1 The Science of Biology
2 The Chemistry of Life
Unit Project
UNIT 2 Ecology
3 The Biosphere
4 Ecosystems and Communities
5 Populations
6 Humans in the Biosphere
Unit Project
UNIT 3 Cells
7 Cell Structure and Function
8 Photosynthesis
9 Cellular Respiration and Fermentation
10 Cell Growth and Division
Unit Project
UNIT 4 Genetics
11 Introduction to Genetics
12 DNA
13 RNA and Protein Synthesis
14 Human Heredity
15 Genetic Engineering
Unit Project
UNIT 5 Evolution
16 Darwin's Theory of Evolution
17 Evolution of Populations
18 Classification
19 History of Life
Unit Project
UNIT 6 From Microorganisms to Plants
20 Viruses and Prokaryotes
21 Protists and Fungi
22 Introduction to Plants
23 Plant Structure and Function
24 Plant Reproduction and Response
Unit Project
UNIT 7 Animals
25 Introduction to Animals
26 Animal Evolution and Diversity
27 Animal Systems I
28 Animal Systems II
29 Animal Behavior
Unit Project
UNIT 8 The Human Body
30 Digestive and Excretory Systems
31 Nervous System
32 Skeletal, Muscular, and Integumentary Systems
33 Circulatory and Respiratory Systems
34 Endocrine and Reproductive Systems
35 Immune System and Disease
Unit Project
A Visual Guide to The Diversity of Life
HOW TO USE THIS GUIDE
THE TREE OF LIFE
Bacteria
Protists
Fungi
Plants
Animals
Appendices
Appendix A Science Skills
Appendix B Lab Skills
Appendix C Technology & Design
Appendix D Math Skills
Appendix E Periodic Table
Glossary
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q, R
S
T
U
V
W
X, Y, Z
Index
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Credits
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