BIO 202 Exam #4 - Bradley University

Are viruses small or large?

Small

Are viruses cellular or non-cellular

Non-cellular

Are viruses sensitive to anti-biotics?

No

Viruses are

obligate intracellular parasites

What does the virus have to fit in with?

Host cell's metabolism

Do viruses contain both DNA and RNA or only DNA or RNA?

DNA or RNA

What is the name of the protein coat that viruses have?

Capsid

Do viruses have a cell membrane?

No, potentially an envelope

For attatchments, what do viruses have?

Virally-encoded proteins

How do viruses replicate?

Very fast, repeatedly

How many classifications can viruses be categorized by?

4

Viruses are classified by

Nucleic acid, capsid, envelope, and mode of replication

Virus genomes can be described as

Unique

Virus genome structure looks like

DsDNA —-> mRNA —-> protein

Viral genomes evolve via

Mutation, recombination, and re-assortment

Mutations in viral genomes

Replication errors are very common, RNA does not have proofreading abilities

Recombination in viral genomes

"Cut and paste" of genomes, DNA viruses have high recombination rates

Re-assortment in viral genomes

"Swapping" of genome parts

Is it good for a viral genome to become virulent?

Yes, virulence is good

Is it good for a viral genome to become less recognized by IS?

No, it is better to be more recognized by the IS

Is it good for a viral genome to be deliberately lessened?

Yes, it needs to be deliberately lessened

Antigens

Foreign, non-self, outside the cell

What do capsid proteins protect?

The genome

How can you identify capsid proteins?

Serological tests

How do capsid proteins work?

The capsid and envelope bind, and it mediates the release

Spike proteins

Antigenic, put into membranes

Replicate proteins / enzymes

DNA and RNA polymerase

Clinical virus identification

Serological tests, "Antibody associated tests", and nucleic acid tests

Serological tests

Detect antibodies or viral proteins in patients

Antibody-associated tests

ELISA test

Nucleic acid test

PCR

First live vaccine

Polio vaccine

Benefits of live vaccines

More realistic and longer duration

Drawbacks of live vaccines

Can be transmitted and is less stable

Benefits of killed vaccines

Not transmissible and is more stable

Drawbacks of live vaccines

Less effective, less realistic, and shorter duration

Bacterial viruses

Bacteriophages that can attach everywhere

What are the five steps of the lytic cycle?

attachment, penetration, biosynthesis, maturation, release

In the attatchment step of the lytic cycle, what happens?

Attaches via tail fibers to the host cell

In the penetration step of the lytic cycle, what happens?

Phage penetrates cell wall, injects DNA

In the biosynthesis step of the lytic cycle, what happens?

Synthesis of DNA/proteins

In the biosynthesis step of the lytic cycle, what are early genes?

For replication enzymes

In the biosynthesis step of the lytic cycle, what are late genes?

For structural proteins

In the maturation step of the lytic cycle, what happens?

Assembly of phage particles

In the release step of the lytic cycle, what happens?

Enzyme breaks cell wall, liberates phage

Which cycle does the phage causes death?

Lytic cycle

Which cycle integrates the phage?

Lysogenic

What is the main outcome from lysogeny?

Immunity from infection by some virus type, transduction, and lysogenic conversion

All human viruses have a ____________ origin

Animal virus

How can animal viruses grow?

Living animals, fertilized eggs, and cell culture

What are the steps of multiplication in human/animal viruses

Attachment, penetration, uncoating, biosynthesis, maturation, and release

In the attachment step of the multiplication in human/animal viruses, what happens?

Viruses attaches to cell receptor

In the penetration step of the multiplication in human/animal viruses, what happens?

Happens by endocytosis/fusion

In the uncoating step of the multiplication in human/animal viruses, what happens?

Happens by host/viral enzymes

In the biosynthesis step of the multiplication in human/animal viruses, what happens?

Synthesis of nucleic acid

In the biosynthesis step of the multiplication in human/animal viruses, what are early genes?

Replication

In the biosynthesis step of the multiplication in human/animal viruses, what are late genes?

Structural proteins

In the maturation step of the multiplication in human/animal viruses, what happens?

Assemble nucleic acid and capsid

In the release step of the multiplication in human/animal viruses, what happens?

By budding or lysis

In the release step of the multiplication in human/animal viruses, what is budding?

Releasing in an enveloped virus

In the release step of the multiplication in human/animal viruses, what is lysis?

Releasing in a naked virus

What are the two main biosynthesis strategies?

Genome replication and protein synthesis

What is used in genome replication?

Viruses use replicase

What does protein synthesis depend on

DNA or RNA

DNA viruses are typically formed as

DsDNA

Where do DNA viruses replicate?

Host cell's nucleus (except for pox virus)

Do DNA viruses encode their own replicase or another cells?

They encode their own replicase

Where do RNA viruses replicate?

Host cell's cytoplasm (except for retroviruses and influenza)

Do RNA viruses encode their own replicase or another cells?

They encode their own replicase

What does RNA typically come formed as?

ssRNA

Positive polarity refers to

Using mRNA as a protein

Negative polarity works like

Strand 1 starts negative, gets turned into mRNA (+), and then transcribed into the genome and turned back negative

HIV related ssRNA-RT

2 copies of single stranded RNA,with positive polarity

What are the 3 ways animal viruses get spread?

- vertical

- horizontal

- animal —> human

Vertical animal virus transmission

Parent —> offspring

Horizontal animal virus transmission

Peer —> peer (within a population)

How can you contract enveloped viruses?

Via physical contact

How can you contract non-enveloped viruses?

Via feces/orally (EX: polio)

Pathogenesis means

development of disease

Does pathogenesis at the cellular level have a morphology change?

No

Cytopathic effects

Occur at the cellular level of pathogenesis, includes tumors, death,and fusion

Pathogenesis at the organismal level interferes with ______ ________

Organ function

Are toxins encoded when speaking about pathogenesis?

No

Genome changes affect what 3 things?

Host cell specificity, antigenic variation, and viral drug resistance

Non-specific responses

Fever, phagocytosis, NK cells, and interferons

Specific responses differ based on

The location of the virus

Extracellular specific reponses

Antibodies (immunoglobulins)

Intracellular specific responses

Tc (cytotoxic cells)

How do viruses escape immune detection?

Antigenic variation and intracellular life style

HIV stands for

human immunodeficiency virus

HIV-1

worldwide, more transmissible

HIV-2

Mostly located in West Africa

HIV causes a loss in

Cell-mediated immune reponses

HIV-secondary infections are commonly referred to as

Opportunistic infections

AIDS was first identified in

1981

Host cell specificity refers to

Th cells and macrophages

Host cell specificity uses what viral proteins?

gp120 and gp41

gp120 and gp41 have to have

Co-receptors

What is an example of a receptor that can be used as a co-receptor?

CD4

HIV genome contains

2 strands of positive polarity single stranded RNA