Section 1 Viral Structure and Replication Chapter 24 Objectives • Summarizethe discovery of viruses. • Describewhy viruses are not considered living organisms. • Describethe basic structure of viruses. • Comparethe lytic and lysogenic cycles of virus replication. • Summarizethe origin of viruses.

Section 1 Viral Structure and Replication Chapter 24 Discovery of Viruses • Researchers in the late 1800s discovered that something smaller than bacteria could cause disease. • In 1935, ________________ ______________ demonstrated that viruses were not cells when he crystallized _______, the virus that causes tobacco mosaic disease in tobacco and tomato plants.

Section 1 Viral Structure and Replication Chapter 24 Characteristics of Viruses • Viruses do not have all of the characteristics of life and are therefore

Section 1 Viral Structure and Replication Chapter 24 Characteristics of Viruses, continued • Viral Size and Structure • Viruses are nonliving particles containing DNA or RNA and are surrounded by a protein coat called a ______________________. • Some viruses also have an _______________ that is derived from a host cell’s nuclear membrane or cell membrane.

Section 1 Viral Structure and Replication Chapter 24 Characteristics of Viruses, continued • Classification of Viruses • Viruses can be classified based on whether they have __________ or _________, whether the RNA or DNA is _____________ or ____________ stranded and ______________ or ____________, by ____________ ______________, and whether or not they have an ___________________.

Section 1 Viral Structure and Replication Chapter 24 Viral Replication, continued • Replication in DNA Viruses • DNA viruses can enter host cells and directly produce RNA, or they can insert into a host’s chromosome, where they are

Section 1 Viral Structure and Replication Chapter 24 Viral Replication, continued • Replication in RNA Viruses • The RNA genome of some RNA viruses can be • ____________________ use ____________ ___________________ and RNA as a template to make DNA, which is then used to produce viral RNA and proteins.

Section 1 Viral Structure and Replication Chapter 24 Viral Replication, continued • Replication in Viruses That Infect Prokaryotes • Bacteriophages are

Section 1 Viral Structure and Replication Chapter 24 Viral Replication, continued • Lytic Cycle • Viruses can follow a lytic cycle, making new viral particles immediately.

Section 1 Viral Structure and Replication Chapter 24 Viral Replication, continued • Lysogenic Cycle • Viruses can follow a lysogenic cycle, becoming part of the host genome and making new particles later.

Section 1 Viral Structure and Replication Chapter 24 The Lytic and Lysogenic Cycles

Section 1 Viral Structure and Replication Chapter 24 Viral Replication, continued • Viruses: Tools for Biotechnology • Viruses are important tools for biotechnology.

Section 1 Viral Structure and Replication Chapter 24 The Origin of Viruses • Most scientists think viruses originated from

Section 2 Viral Diseases Chapter 24 Objectives • Nameseveral vectors of viral diseases. • Identifyfour viral diseases that result in serious human illnesses. • Discuss the relationship between viruses and cancer. • Namethree examples of emerging viral diseases. • Comparethe effectiveness of vaccination, vector control, and drug therapy in fighting viruses. • Contrastviroids, prions, and viruses.

Section 2 Viral Diseases Chapter 24 Vectors of Viral Diseases • Vectors, or hosts, of viral diseases include

Section 2 Viral Diseases Chapter 24 Human Viral Diseases • Viruses cause many human diseases, including the

Section 2 Viral Diseases Chapter 24 Human Viral Diseases, continued • Chickenpox and Shingles • Chickenpox and shingles are caused by the same varicella-zoster herpesvirus.

Section 2 Viral Diseases Chapter 24 Human Viral Diseases, continued • Viral Hepatitis • Hepatitis, or inflammation of the liver, can be caused by at least five viruses. • Hepatitis A and hepatitis E can be spread by • Hepatitis B, C, and D are spread by

Section 2 Viral Diseases Chapter 24 Human Viral Diseases, continued • Acquired Immune Deficiency Syndrome (AIDS) • The human immunodeficiency virus (HIV) is an RNA virus spread by sexual contact, by contact with infected body fluids, and from mother to fetus. • HIV targets _____________________ and thus damages the body’s immune system. The disease called acquired immune deficiency syndrome (AIDS) results.

Section 2 Viral Diseases Chapter 24 AIDS (Acquired Immunodeficiency Syndrome)

Section 2 Viral Diseases Chapter 24 Human Viral Diseases, continued • Viruses and Cancer • Some viruses contain _________________ that can cause cancer, while other viruses convert___________________________, which usually control cell growth,tooncogenes.

Section 2 Viral Diseases Chapter 24 Emerging Viral Diseases • Emerging viruses usually infect animals isolated in nature but can jump to humans when

Section 2 Viral Diseases Chapter 24 Prevention and Treatment • Vaccinations • A vaccine contains a harmless version of a virus, bacterium, or a toxin that causes • Vaccines have helped to greatly reduce certain viral diseases.

Section 2 Viral Diseases Chapter 24 Prevention and Treatment, continued • Vector Control • Control efforts, including killing mosquitoes and other vectors and quarantining ill patients, have helped reduce the spread of certain viral diseases.

Section 2 Viral Diseases Chapter 24 Prevention and Treatment, continued • Drug Therapy • _____________________ are ineffective against viral diseases. • Viral drugs, such as acyclovir, block

Section 2 Viral Diseases Chapter 24 Virods and Prions • ____________________ are short, circular, single strands of RNA lacking a capsid that infect plant cells. • _____________________ are infectious particles containing protein but no nucleic acids. • Prions cause mad cow disease and similar degenerative brain diseases.

Section 2 Viral Diseases Chapter 24 Important Viral Diseases

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