Chapter 27 Viruses
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