Questions and Answers

What is the definition of a virus?

A submicroscopic, parasitic, filterable agent consisting of nucleic acid: DNA or RNA surrounded by a protein coat.

What is the definition of a bacterium?

Prokaryotic organism characterized by peptidoglycan cell walls.

What is a viral species?

Group of viruses sharing the same genetic information and ecological niche.

What is virology?

Study of viruses. Signup and view all the answers

Which of the following are general characteristics of viruses? (Select all that apply)

Filterable: can pass through bacterial filters Signup and view all the answers

What is the protein coat of a virus called?

Capsid. Signup and view all the answers

What is the capsid made up of?

Capsomeres, which are protein subunits. Signup and view all the answers

What determines the host range of a virus?

Specific host attachment sites and cellular factors. Signup and view all the answers

The capsid is made up of and surrounds ______.

proteins, DNA or RNA Signup and view all the answers

What is the envelope of a virus made up of?

Cell membrane or vesicles, a combination of lipids, proteins, and carbohydrates. Signup and view all the answers

Some enveloped viruses are covered in __________.

Spikes. Signup and view all the answers

What are non-enveloped viruses known for?

They are more difficult to kill. Signup and view all the answers

What is tissue tropism?

Tissue specificity or specific tissue attachment. Signup and view all the answers

What is the smallest virus?

Rhinovirus. Signup and view all the answers

Bacteriophages enter the cell.

False Signup and view all the answers

What is a virion?

Complete fully developed viral particle. Signup and view all the answers

What is a helical virus and provide an example.

Resemble long rods that may be rigid or flexible. Example: Rabies and Ebola. Signup and view all the answers

What is a polyhedral virus and provide an example.

Many-sided virus and the capsid is a polyhedron. Example: Herpes Simplex Virus and Poliovirus. Signup and view all the answers

Enveloped viruses are typically , an example is .

spherical, Herpes Simplex Virus Signup and view all the answers

What are plaques?

A clearing in a bacterial lawn resulting from lysis by phages. Signup and view all the answers

What is herpesviridae?

100 known viruses, DNA virus, named after the spreading appearance of cold sores. Signup and view all the answers

What is Picornaviridae?

Single stranded RNA virus. Signup and view all the answers

What is Retroviridae?

RNA virus that carries reverse transcriptase. Signup and view all the answers

What is reverse transcriptase?

Uses viral RNA as a template to produce complementary double stranded DNA. Signup and view all the answers

What are the 7 groups of genome-based virus classification? (Select all that apply)

(-) ssRNA virus Signup and view all the answers

What is a dsDNA virus and give an example.

Double stranded DNA virus. Example: Herpesvirus, Adenovirus. Signup and view all the answers

What is an ssDNA virus and give an example.

Single stranded DNA virus. Example: Parvoviruses. Signup and view all the answers

What is a dsRNA virus and give an example.

Double stranded RNA virus. Example: Reovirus. Signup and view all the answers

What is a (+)ssRNA virus and give an example.

Positive single strand RNA virus. Example: Picornavirus. Signup and view all the answers

What is a (-)ssRNA virus and give an example.

Negative single strand RNA virus. Example: Rhabdovirus. Signup and view all the answers

What is an ssRNA-RT virus and give an example.

Single stranded RNA, can replicate DNA from RNA. Example: Retroviruses. Signup and view all the answers

Give an example of a dsDNA-RT virus.

Hepadnavirus. Signup and view all the answers

Viral envelopes closely resemble __________.

eukaryotic cell membranes Signup and view all the answers

Viruses must be grown in __________.

living cells Signup and view all the answers

of plaques in a lawn growth is equivalent to ______.

<h1>of viruses in the culture</h1> Signup and view all the answers

Animal viruses can be cultured in: (Select all that apply)

Living animals Signup and view all the answers

Viruses can be identified by: (Select all that apply)

Cytopathic effects Signup and view all the answers

What does serological testing detect in identifying viruses?

Detects antibodies against the virus in the patient. Signup and view all the answers

What is viral multiplication?

<ol> <li>Obligate intracellular parasites use the host cells' machinery. 2) Very limited number of genes encode proteins for capsids, viral nucleic acid replication and movement. 3) Kills or lives in harmony within the host cell.</li> </ol> Signup and view all the answers

Outside the cell, viruses are __________.

inert Signup and view all the answers

What are the two types of bacteriophage multiplication? (Select all that apply)

Lysogenic cycle Signup and view all the answers

What is the lytic cycle?

Phage multiplies eventually causing lysis and death of the host cell. Signup and view all the answers

What are the stages of the lytic cycle?

<ol> <li>Attachment 2) Penetration 3) Biosynthesis 4) Maturation 5) Release.</li> </ol> Signup and view all the answers

What happens during the attachment stage of the lytic cycle?

Attaches to cell surface receptors, chance encounter, no active movement. Signup and view all the answers

What occurs during the penetration stage of the lytic cycle?

Only the genome enters; bacteriophage injects nucleic acid into the bacterium. Signup and view all the answers

What does biosynthesis entail in the lytic cycle?

Production of the phage DNA and proteins. Signup and view all the answers

What is maturation in the lytic cycle?

Assembly to form intact phage. Signup and view all the answers

What happens during the release stage of the lytic cycle?

Host cell lyses and new virions are released. Signup and view all the answers

How do some animal viruses exit the host cell?

By budding. Signup and view all the answers

What are the stages of the lysogenic cycle?

<ol> <li>Attachment 2) Penetration 3) Recombination 4) Cell division 5) Occasionally can excise and enter lytic cycle.</li> </ol> Signup and view all the answers

What occurs during the attachment stage of the lysogenic cycle?

Attaches to cell surface receptors, chance encounter, no active movement. Signup and view all the answers

What happens during the penetration stage of the lysogenic cycle?

Only the genome enters; bacteriophage injects nucleic acid into the bacterium. Signup and view all the answers

What is recombination in the lysogenic cycle?

Phage DNA integrates within the bacterial chromosome by recombination becoming a prophage. Signup and view all the answers

What happens during the cell division stage of the lysogenic cycle?

Lysogenic bacterium reproduce normally. Signup and view all the answers

What might happen during the lysogenic cycle?

Rare event, spontaneous that can lead to the phage DNA popping out and initiating the lytic cycle. Signup and view all the answers

What is a prophage?

Phage DNA inserted into the host cell's DNA. Signup and view all the answers

Place in order found in the host cell from a bacteriophage: 1: capsid protein 2: infective phage particles 3: phage nucleic acid.

3, 1, 2 Signup and view all the answers

All viruses have a __________.

capsid Signup and view all the answers

Bacteriophages never have an __________.

envelope Signup and view all the answers

The most basic virion structure is ______________.

nucleocapsid Signup and view all the answers

What do RNAse and DNAse enzymes do?

Break down RNA or DNA; capsids protect viruses from being broken down. Signup and view all the answers

What is a provirus?

Viral DNA that is integrated into the host cell's DNA. Signup and view all the answers

What is the genus responsible for causing HIV/Aids?

Lentivirus. Signup and view all the answers

What is oncology?

Study of cancer. Signup and view all the answers

What is the difference between benign and malignant tumors?

Benign tumors do not metastasize or spread. Signup and view all the answers

What are three important characteristics of cancer cells? (Select all that apply)

Dedifferentiation of cells Signup and view all the answers

What is carcinoma?

Cancer of epithelial tissue. Signup and view all the answers

What is sarcoma?

Cancer of connective tissue usually the blood. Signup and view all the answers

What happens to the genetic material of oncogenic viruses?

It becomes integrated into the host cell's DNA (provirus). Signup and view all the answers

What is an oncogenic virus?

Virus capable of inducing tumors. Signup and view all the answers

What is an oncogene?

A gene that brings about malignant transformation. Signup and view all the answers

What is a proto-oncogene?

Normal cellular gene that turns up the cell cycle, used for balance. Signup and view all the answers

What is a tumor suppressor gene?

Inhibits the cell cycle. Signup and view all the answers

What are the two genes that regulate the cell cycle? (Select all that apply)

Proto-oncogenes Signup and view all the answers

What type of virus is a cancer inducing virus?

DNA virus. Signup and view all the answers

Name the one RNA virus that can cause cancer.

HIV. Signup and view all the answers

What do activated oncogenes do?

Transform normal cells into cancerous cells. Signup and view all the answers

What does transformation regarding viruses and cancer mean?

The changing of a normal cell into a cancerous cell. Signup and view all the answers

What is a tumor specific transplantation antigen (TSTA)?

Viral antigen on the surface of the transformed cell. Signup and view all the answers

What is an example of an oncogenic DNA virus?

Papilloma Virus. Signup and view all the answers

What is another example of an oncogenic DNA virus?

Hepatitis B. Signup and view all the answers

What is an example of an oncogenic DNA virus that affects AIDS patients?

HHV-8 Kaposi's Sarcoma. Signup and view all the answers

What is an example of an oncogenic DNA virus that can cause Burkitt's Lymphoma?

Epstein-Barr Virus (EBV). Signup and view all the answers

What is an example of an oncogenic RNA virus?

Hepatitis C (HCV). Signup and view all the answers

What is another example of an oncogenic RNA virus?

Human T-cell leukemia virus (HTLV-1). Signup and view all the answers

How can proto-oncogenes be activated to become oncogenes and cause cancer? (Select all that apply)

Spontaneous mutation Signup and view all the answers

What is a latent infection?

Condition in which the pathogen remains in the host for long periods without producing disease. Signup and view all the answers

What is a chronic infection?

An illness that develops slowly and is likely to continue or recur for long periods of time. Signup and view all the answers

Give an example of a latent infection.

Herpes virus. Signup and view all the answers

Give an example of a chronic infection.

AIDS/HIV. Signup and view all the answers

What is a prion?

Small proteinaceous infectious particle. Signup and view all the answers

How can prions be transmitted?

Inherited or transmitted by ingestion, transplants, and surgical instruments. Signup and view all the answers

What is the difference between encephalopathy and encephalitis?

Encephalopathy: Brain is deteriorating causing holes in the brain. Signup and view all the answers

What are causes of spongiform encephalopathy? (Select all that apply)

Sheep scrapie Signup and view all the answers

What is PrPc?

Normal cellular prion protein, found on the cell surface and is involved with cell death. Signup and view all the answers

What is PrPsc?

Scrapie protein that accumulates in brain cells and forms plaques. Signup and view all the answers

Study Notes

Virus Characteristics

A virus is a submicroscopic, parasitic agent composed of nucleic acid (DNA or RNA) surrounded by a protein coat (capsid).
Obligatory intracellular parasites depend on host cells for replication.
They can pass through bacterial filters, indicating their small size.
Viruses may have an envelope originating from a host cell's membrane, and they often exhibit tissue specificity.

Virus Structure

The capsid consists of protein subunits called capsomeres and encases the viral nucleic acid.
Envelopes are composed of a phospholipid bilayer and may contain spikes made of carbohydrate-protein complexes that aid in host attachment.
Non-enveloped viruses are more resilient to environmental factors.

Virus Types and Examples

Helical viruses (e.g., Rabies, Ebola) appear as long rods, while polyhedral viruses (e.g., Herpes Simplex Virus, Poliovirus) have many sides.
Enveloped viruses are generally spherical, exemplified by Herpes Simplex Virus.
Varsity of viruses include ssRNA (e.g., Picornavirus) and dsDNA viruses (e.g., Herpesvirus, Adenovirus).

Viral Multiplication Phases

Viruses must be grown in living cells, as they are inert outside a host.
Two primary multiplication cycles for bacteriophages exist: lytic (results in cell lysis) and lysogenic (integrates viral DNA into host DNA).
In the lytic cycle, stages include attachment, penetration, biosynthesis, maturation, and release of new virions.

Cancer and Oncogenic Viruses

Oncogenic viruses can induce tumor formation by integrating their genetic material into the host DNA.
Key characteristics of cancer cells include rapid division, loss of anchoring and inhibition of contact, leading to metastasis.
Oncogenic DNA viruses include Papilloma Virus (HPV, causes cervical cancer) and Hepatitis B (liver cancer).
HIV is a notable RNA virus associated with cancer induction.

Prions Overview

Prions are infectious particles consisting solely of protein, characterized by abnormal folding.
They can be inherited or transmitted through ingestion, surgeries, or transplants.
Prion diseases, like Creutzfeldt Jakob Disease and Mad Cow Disease, cause spongiform encephalopathies resulting in brain degeneration.

Additional Concepts

Latent infections, like those caused by herpes viruses, persist without symptom production for long periods.
Chronic infections, exemplified by AIDS/HIV, develop slowly and can recur.
Proto-oncogenes regulate normal cell division; activation by factors like carcinogens or viral infections can transform them into oncogenes, which lead to cancer.

Research & Testing

Viruses are identified using cytopathic effects, serological testing (detects antibodies), and nucleic acid analysis.
The presence of tumor-specific transplantation antigens can signal transformed cells due to oncogenic viruses.

Summary

Viruses and prions represent unique classes of infectious agents, each with distinct structures, multiplication mechanisms, and implications for health, especially in relation to cancer and chronic diseases. Understanding their characteristics aids in advancements in virology and treatment options.

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Explore key definitions and concepts related to viruses and prions in this flashcard quiz based on Chapter 13 of Microbiology. Learn about the characteristics of viruses, bacteria, and viral species while enhancing your understanding of microbiological principles.

Microbiology Chapter 13: Viruses and Prions Flashcards