Micro Lecture Exam #2

What is a vector?

A living organism that transmits a pathogen between hosts

Which is the largest phylum in the animal kingdom?

Arthropoda

What three body features characterize arthropods?

Segmented bodies
Hard exoskeleton
Jointed legs

How many legs do adult arachnids have?

8 legs

Which animals are examples of arachnids?

Spiders
Mites
Ticks

How many antennae do crustaceans have?

4 antennae arranged in 2 pairs

Which animals are examples of crustaceans?

Crabs
Crayfish
Lobsters

How many legs do insects have?

6 legs

Which animals are examples of insects?

Bees
Flies
Lice

How does a mechanical vector transmit a pathogen?

Physically carries the pathogen without requiring its development or multiplication inside the vector

How does a biological vector transmit a pathogen?

The pathogen develops, multiplies, or both inside the vector before transmission

What is a vectorborne disease?

A disease transmitted through a vector

What is a viroid?

An infectious RNA molecule

What is a prion?

An infectious abnormal protein

Why are viruses considered obligate intracellular parasites?

They lack the cellular machinery to replicate independently and must use a living host cell

What type of nucleic acid makes up a viral genome?

A single type of nucleic acid: either DNA or RNA

What surrounds a virus’s nucleic acid?

A protein coat

What is a viral envelope?

What does the viral envelope consist of?

An additional outer covering surrounding the protein coat. Present in some viruses, including some animal viruses
-Contains proteins, lipids, and carbohydrates

Where does each component of a viral envelope come from?

Proteins: viral origin
Lipids and carbohydrates: host cell’s plasma membrane

What does a virus direct its host cell to produce?

The components needed to make new viruses

What types of cells can different viruses infect?

Plant cells
Bacterial cells
Animal cells
Human cells

What is a virus’s host range?

The spectrum of host cells it can infect

Which bacterial structures can provide attachment sites for viruses?

Cell wall
Flagella
Fimbriae

How do host-cell receptors help a virus begin infection?

The receptors allow matching viral structures to attach to the cell

Where are viral receptors located on animal and human cells?

On the cell membrane

What is a bacteriophage? What is it also known as?

A virus that infects bacterial cells
Also called a phage

What is phage therapy?

Using bacteriophages to treat bacterial infections

What is an oncolytic virus?

A virus that infects and destroys cancer cells

What is an oncogenic virus?

A virus that can contribute to the development of cancer

Where are viral attachment sites located on plant cells?

Cell wall

Name an example of a larger virus

Vaccinia virus

What is a virion?

A fully assembled infectious virus particle

What are the four possible nucleic-acid and strand combinations for viral genomes?

Single-stranded DNA
Double-stranded DNA

Single-stranded RNA
Double-stranded RNA

How do linear and circular viral genomes differ?

Linear genomes have two ends
Circular genomes form closed loops

What is a segmented viral genome?

A genome divided among separate nucleic-acid molecules

What percentages of influenza virus are nucleic acid and viral protein?

Nucleic acid: 1%
Viral proteins: 99%

What percentages of a bacteriophage are nucleic acid and viral protein?

Nucleic acid: 50%
Viral proteins: 50%

What is a genome?

The complete set of genetic information in an organism or virus

A tick transmits a pathogen after the pathogen develops inside it. Identify the tick’s arthropod group and vector type.

Arachnida
Biological vector

A virus cannot bind to the receptors on a particular animal cell. Which step needed for infection is affected?

Attachment to the host cell

A virus has genetic material surrounded by a protein coat but lacks an additional outer membrane. Which viral structure is absent?

An envelope

A viral genome consists of several separate RNA molecules, each containing one chain with two free ends. Describe its strand count, shape, and genome organization.

Single-stranded
Linear
Segmented

A treatment uses viruses to infect and destroy disease-causing bacteria. What is this treatment called, and what are the viruses called?

Phage therapy
Bacteriophages

How do nonsegmented and segmented viral genomes differ?

Nonsegmented: genetic information in one continuous nucleic-acid molecule

Segmented: genetic information divided among several separate nucleic-acid molecules

What is the scientific name for a virus’s protein coat?

Capsid

What are the subunits that make up a viral capsid called?

Capsomeres

What does a viral capsid surround?

The viral nucleic acid

What is the difference between nucleic acid and a genome?

Nucleic acid is the genetic material—DNA or RNA

A genome is the complete set of genetic instructions carried in that material

Which cell produces the viral proteins incorporated into a viral envelope?

The host cell

Which components of a viral envelope come from the host cell’s plasma membrane?

Lipids
Carbohydrates

How do enveloped animal viruses obtain their envelope?

Through budding
The virus buds through the host cell’s membrane, taking a portion of it as its envelope

Do all animal viruses have an envelope?

No
Animal viruses may be enveloped or non-enveloped

What may happen to the host cell after an enveloped virus leaves by budding?

The host cell may survive or die

What happens to the host cell when non-enveloped viruses are released through cell rupture?

The host cell is destroyed

What is hemagglutination?

Clumping of red blood cells

Which virus can cause hemagglutination?

Influenza virus

What are two functions of viral spikes?

Attachment to host cells
Identification of the virus

What structural feature forms the basis for describing viral morphology?

The architecture of the capsid

What four structural descriptions are used to describe viral morphology?

Helical
Polyhedral
Enveloped
Complex

What shape characterizes a helical viral capsid, and where is its nucleic acid located?

A cylindrical structure with a hollow central region
The nucleic acid lies within the helical protein structure

Which two viruses are examples of helical viruses?

Rabies virus
Ebola virus

What does polyhedral mean?

Many-sided

What capsid shape do poliovirus and adenovirus have, and how are its faces arranged?

Polyhedral
20 equilateral triangular faces

Which two viruses are examples of polyhedral viruses?

Poliovirus
Adenovirus

What two capsid arrangements can be surrounded by a viral envelope?

Helical
Polyhedral

What structural description applies to herpes simplex virus?

Enveloped polyhedral virus

What structural descriptions apply to influenza virus?

Enveloped spiked helical virus

What does complex morphology mean for a virus?

Its overall structure does not fit a simple helical or polyhedral form

Which two viruses are examples of complex viruses?

T-even bacteriophages
Smallpox virus

What surrounds the nucleic acid in the complex structure of smallpox virus?

Multiple protein coats (layers)

What genus includes smallpox virus?

Orthopoxvirus

Which committee oversees viral classification and naming? and what is the acronym for it?

International Committee on Taxonomy of Viruses

ICTV

What is a virologist?

A scientist who studies viruses

What three characteristics are used to classify and name viruses?

Nucleic acid type
Strategy for replication
Morphology

What suffix identifies a viral genus, and what is an example of a genus name?

-virus
Simplexvirus

What suffix identifies a viral family, and what is an example of a family name?

-viridae
Herpesviridae

What suffix identifies a viral order?

-virales

What is a viral species?

A group of related viruses sharing characteristics such as host range or ecological niche

What is the taxonomic relationship between HIV-1 and HIV-2?

They belong to different species within the same genus

A virus produces capsomeres, but they cannot assemble together. Which complete viral structure would fail to form?

The capsid

A virus produces capsomeres, but they cannot assemble together. Which complete viral structure would fail to form?

The capsid

Influenza particles link red blood cells into clumps. Identify the phenomenon and the viral surface structures involved

Hemagglutination
Viral spikes

A virus leaves its host cell by budding. Does this guarantee that the host cell survives? Explain

No
The host cell may survive, but survival is not guaranteed

What is a chromosome?

A long DNA molecule packaged with proteins

You encounter the name Adenoviridae. What taxonomic rank does it represent?

Family

You encounter the name Mononegavirales. What taxonomic rank does it represent?

Order

You encounter the name Lymphocryptovirus as a taxonomic group. What rank does its ending suggest?

Genus

You encounter the name Hepadnaviridae. What taxonomic rank does it represent?

Family

Which represents the broader group: order or family?

Order

You encounter the taxonomic name Simplexvirus. What rank does it represent?

Genus — recognized by the ending -virus

What is a carcinoma?

Cancer that starts in epithelial cells—the cells that cover surfaces and line organs and cavities.

What is an enzyme?

A biological catalyst that speeds up a chemical reaction without being used up.

Who is credited with discovering a human cancer-causing virus, and in what year?

Sarah Stewart
1972

What underlying change can transform a normal cell into a cancer cell?

Genetic mutations that disrupt normal cell-growth controls.

What changes in chromosome number can occur in transformed cancer cells?

An increase or decrease in chromosome number.

What are oncogenes?

Genes that can promote uncontrolled cell growth and cancer.

Where did the genes that became viral oncogenes originally come from?

Animal cells

What cell-surface change can accompany tumor transformation?

Altered surface antigens

How is cell division altered during tumor formation?

Increased, unregulated mitosis

What three structural features characterize a benign tumor?

Uniform cells
Well-defined borders
A surrounding capsule