Chapter 27 Viruses

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In AIDS patients, the virus homes in on the _____ T cells

CD4+

Are viruses and bacteria the only infectious agents found in plants and animals?

No

What enzyme is required to replicate HIV?

Reverse transcriptase

Prophage

The DNA segment that is integrated into a host cell's genome

The CD8+ cell antiviral factor (CAF) is used to

block replication of the HIV virus

Typically viruses form _______around their nucleic acid

capsid

Each HIV particle possesses a glycoprotein called ________on its surface

gp120

The only structural pattern to be found among isometric viruses is

icosohedral

When a virus is integrated into a cellular genome it is called a

lysogenic virus

A person infected with HIV may not develop AIDS if the virus has the defective _____ gene.

nef

Viruses are considered to be

non-living

When a bacteriophage is integrated into a cellular genome it is called a

prophage

Capsid

protein sheath that viruses form around their nucleic acid core

Host range

the suitable cells for a particular virus

The first virus to be purified was the

tobacco mosaic virus

The genetic alteration of a cell's genome is called

transformation

Bacteriophages

viruses that infect bacteria, they are large and complex with relatively large amounts of DNA and proteins

The basic structures of a virus are:

*Helical: rodlike or threadlike appearance *Icosahedral: soccer ball shape with 20 equilateral triangular facets *Binal: complex twofold, symmetry that is neither purely icosahedral or helical *Polymorphic: have no distinctive symmetry example includes influenza

An example of an emerging virus is

Ebola

The most lethal virus is

Ebola

Viruses that originate in one organism and then pass to another and cause disease are called ________

Emerging viruses

_______is the virus causing fever blisters

Herpes simplex

Envelope

Many animal viruses have an *envelope* around the capsid that is rich in proteins, lipids, and glycoproteins

HIV is a ______virus.

RNA

Retrovirus

Special class of RNA viruses that have an RNA genome that is reverse-transcribed into DNA by the enzyme reverse transcriptase; Ex: HIV is a retrovirus

How do retroviruses differ from other viruses?

They can convert their RNA into DNA

In influenza what are the types

Type A (most dangerous) and Types B and C (rarely cause health problems)

Phage conversion

When the phenotype or characteristics of the lysogenic bacterium is altered by the prophage

The basic structure of a virus contains:

a nucleic acid and a protein coat (no cell wall)

A lysogenic cycle involves

a period of genome integration

In HIV infection cycle, the HIV enveloped virus does not directly rupture and kill the cell it infects. Instead the new viruses are released from the cell by budding which is ________

a process like exocytosis

Hantavirus

a single stranded RNA virus associated with rodents. Traced to deer mice and is transmitted to humans through fecal and urine contaminated areas

Icosahedron

a structure with 20 equilateral triangular facets

______ may prevent HIV replication by binding with the CXCR4 and CCR5 receptors.

chemokines

Which is not a viral disease?

diphtheria

Viruses are most conveniently thought of as

fragments of genomes

When a virus kills the host cell in which it is replicating, the reproductive cycle is called a

lytic cycle

The infectious substance of prions is

protein

Influenza subtypes differ in their

protein spikes

Copying the HIV virus nucleic acid depends on

reverse transcriptase

The viral enzyme, ____causes the host cell to synthesize a double strand of DNA complementary to the viral RNA.

reverse transcriptase

______are the small naked fragments of RNA that infect plant cells

viroids

Viruses that cause lysis in a host cell are called

virulent viruses


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