In this section you were introduced to the term virus, which is derived from the Latin word that means poison. You discovered that the structure of a typical virus is made up of a protein coat called the capsid and a core that contains nucleic acids (DNA or RNA). The core of a virus may contain DNA or RNA but never both. Bacteriophages, or viruses that infect bacteria, are made up of a head region containing the capsid and core, as well as a tail. The virus to attach itself to a bacterium uses the tail fibers.

In order to reproduce, a virus must invade, or infect, a living cell in a host organism. Typically, a virus becomes attached to a host Cell. The nucleic acids (DNA or RNA) within the viral core are injected into the host cell. What happens next depends on the type of virus and its life cycle. In a lytic infection, the nucleic acid from the virus takes over the host cell and uses the materials of the host cell to make thousands of copies of its own protein coat and nucleic acid. Soon the host cell is filled with viruses and the host cell bursts, or lysis, releasing the viruses to infect other cells in the host.

In a Lysogenic infection, the virus does not reproduce immediately after infecting the host cell. Instead, the nucleic acid of the virus is inserted into the DNA of the host cell. The viral DNA may stay within the host DNA for quite some time. However, eventually it may become active, remove itself from the host DNA, and begin to direct the production of new viruses. As with a lytic infection, the viruses from a Lysogenic infection will burst out of the host cell and are then freed to infect other cells.

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How are viruses classified according to nucleic acid? Give an example of a virus from each type.

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List seven characteristics of viruses.

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What is a virus?

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Name the two types of viruses.

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What is the purpose of extensions, filaments, and tails?

List the five characteristics used to classify viruses. a.

What are the four basic shapes of viruses?

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________________________ A bacterium common to the human intestine

A disease results whenever [A]viruses invade living cells. [B]a viral infection affects the host. [C]bacteria invade living cells. [D]bacteria require nutrients and energy.

A free virus particle is a virion. Which stage in Figure on Page 2 shows the assembling of new virions?

T or F: A particle made up of a nucleic acid core and a protein coat called a capsid

________________________ A portion of the nasal passage where viruses cause the common cold

A protein substance that inhibits virus replication is __. [A]pilus [B]conjugation [C]interferon [D]penicillin

A virus is a particle made up of a nucleic acid core and a protein coat called a ________

________________________ a virus that causes hepatitis

________________________ a virus that destroys its host during replication

________________________ a virus that does not destroy its host during replication

A virus that does not kill its host cell is a(n) __. [A]lytic virus [B]obligate aerobe [C]lysogenic virus [D]obligate anaerobe

________________________ a virus that infects a bacterial cell

T or F: A virus that infects a bacterium is rickettsiae.

________________________ A XXX is the piece of viral nucleic acid that has become part of the host cells DNA.

A(n) XXXX is a virus that infects a bacterial cell. [A]endosperm [B]decomposer [C]plasmid [D]bacteriophage

A(n) XXXX is a virus that infects a bacterial cell. [A]endosperm [B]decomposer [C]plasmid [D]bacteriophage

________________________ Any organism or object that caries or transmits a disease causing organisms

Bacteria cells are not harmed by the prophage they carry until the viral nucleic acid becomes activated and a XXXX begins. ________________________

In any Lysogenic infection, the viral DNA [A]is inserted into the host DNA. [B]destroys the host DNA. [C]replicates repeatedly. [D]is destroyed by the host DNA.

Many viruses are destroyed quickly by the body's XXXX blood cells. _________________

Most viruses that invade the body are killed by __________

Some viruses cause an increase in the XXXX of certain bacteria to antibiotics. __________

T or F: AIDS is a bacterial disease.

T or F: Viruses can be killed by drugs that kill bacteria

T or F: Dimitri Ivonovski found that sap from a plant with the tobacco mosaic virus could cause the disease even after it had been passed through a filter that would normally stop the smallest know organism, a bacterium.

T or F: Edward Jenner developed a vaccine for smallpox.

T or F: Louis Pasteur developed a vaccine for polio.

T or F: Some viral diseases are prevented by vaccines.

T or F: Tumors are solid masses that form when cells pile on top of each other.

T or F: Viral replication changes tumor cells into normal cells.

T or F: Viruses are not thought to be involved in some forms of cancer.

T or F: Viruses have been observed to have prokaryotic characteristics.

T or F: Where and how viruses originated in not known.

The __________________________ was crystallized in 1935.

The first step that is out of order in the life cycle of a lytic virus is that [A]the tail fibers attach to the surface of a bacterium. [B]the virus injects the DNA into the bacterium. [C]the virus makes copies of its protein coat and DNA. [D]a viral gene destroys the DNA of the bacterium.

The life cycle of a lytic virus does not consist of [A]infection. [B]growth. [C]replication. [D]Lysogenic infection.

The piece of viral nucleic acid that has become part of the host cell DNA is called a(n) [A]capsule [B]prophage [C]vector [D]autotroph

The XXXX virus and the XXXX virus remain in the body after the initial infection. ________________________, _____________________________________

Viruses are [A]producers [B]consumers [C]parasites [D]decomposers

Viruses are classified according to ______________ nucleic acid content, the presence or absence of a(n) _____________, the type of ________________ affected, and how they are transmitted.

Viruses are found in XXXX. [A]air [B]water [E]soil [D]all of these

Viruses disrupt the lives of _______________________ they invade.

Viruses do not immediately reproduce and lyse the host cell in a _____________ infection.

Viruses have __ basic shapes. [A]two [B]three [C]four [D]five

Viruses have been observed to have _?_ characteristics. [A]prokaryotic [B]eukaryotic [C]divergent [D]plastic

Viruses have been observed to have XXXX characteristics [A]prokaryote [B]eukaryote [C]divergent [D]plastic

Viruses have XXXX basic shapes. [A]two [B]three [C]four [D]five

Viruses that destroy the host cell during replication are called __. [A]lytic viruses [B]lysogenic viruses [C]obligate viruses [D]pathogenic viruses

What stage of viral replication is occurring when the cell breaks open? [A]entry [B]lysis [C]replication [D]attachment

What stage of viral replication is occurring when the nucleic acid core is injected into the cell [A]attachment [B]entry [C]formation [D]lysis

When Bacteriophages lambda infects E. coli, the [A]bacterial DNA becomes a prophage. [B]viral DNA becomes a prophage. [C]bacterial DNA replicates an lysis. [D]viral DNA replicates and lysis.

Which virus has a spherical envelope with extensions over its surface? [A]tobacco mosaic virus [B]AIDS virus [C]enterovirus [D]Hepatitis B virus

Which virus infect Escherichia coli, a bacterium common in the human intestines. [A]T-4 bacterialphage [B]tobacco mosaic Hepatitis B [D]herpes simplex

XXXX are used in bioengineering research to change bacteria into new useful forms. [A]pili [B]cocci [C]plasmids [D]prophages

XXXX attack an invading virus and attach to it. The virus is destroyed by the antibody or white blood cells

XXXX have become a useful tool for learning about viruses. ________________________

XXXX is a protein substance that inhibits virus replication in an animal cell that has been invaded by a virus. _________________________________________

XXXX is a protein substance that inhibits virus replication in an animal cell that has been invaded by a virus. [A]DNA [B]RNA [C]interferon [D]polio

XXXX studied the tobacco mosaic virus and concluded that the disease is caused by something smaller than bacteria. [A]Edward Jenner [B]Louis Pasteur [C]Dmitri Ivanovski [D]all of these