Micro Chapter 11 Study guide

Rolling Circle replication: - A complementary strand of DNA is synthesized, forming a double strand molecule called replicative form -This is used as a source of both mRNA and genome copies -Several copies are made by semiconservative replication, and phage-specific transcripts are made by transcription off of the negative strand of the replicative form Bacteriophages: -Begins at the origin of replication -uses DNA polymerase, which is a composite protein including one polypeptide encoded by the phage and one by the host -DNA contains terminal repeats at both ends of the molecule and these are eventually used to form concatemers -Transpostion T4 Replication: -Lytic Cycle

Compare and contrast the various types of viral replication.

-ssRNA + Genome is mRNA Single-stranded RNA as its genetic material. The positive-sense viral RNA genome can serve as messenger RNA and can be translated into protein in the host cell. -ssRNA - RNA replicase makes (+) strande used as mRNA and template for more (-) strand genomes

Contrast mRNA production in the two classes of single stranded RNA viruses.

Positive-strand RNA -A nucleic acid strand that has the same sense as the mRNA -can be translated immediately Negative-strand RNA -A nucleic acid strand that has the opposite sense to (is complementary to) the mRNA -Has to be copied before being translated

Distinguish between a positive-strand RNA virus and a negative strand RNA virus.

-Large group of dsDNA viruses that cause diseases like Fever blisters, venereal herpes, chickenpox, shingles, mononucleosis, and cancer -An important group causes clinical forms of cancer (Epstein-Barr virus and Burkitt's lymphoma) -Cytomegalovirus often asymptomatic but can cause pneumonia, retinitis, gastrointestinal diseases -Able to remain latent for extended periods of time -Reactive under stress or weakened immune system

Name at least two common diseases caused by herpesviruses.

-Scrapies in sheep -Mad cow in cows -Chronic wasting disease in deer and elk -Kuru and Creutzfeldt-Jakob disease in humans

Name some prion diseases and the organisms they are found in.

dsRNA virus that affects animals, plants, fungi, and few bacteria ex: rotavirus (diarrea 6-12 month olds) -Others cause respiratory infections or infect plants -Nonenveloped nucleocapsid with a double shell of icosahedral symmetry -Virions contain virus-encoded enzymes necessary to synthesize mRNA and the new RNA genomes -Segmented genome -Binds to receptor, enters and transported into lysosomes, uncoating nucleocapsid, activates RNA replicase in cytoplasm

What are reoviruses?

-Infectious RNA molecules that lack a protein component -Small, circular, ssRNA molecules -Smallest known pathogens -Cause a number of important plant diseases -Do not infect animals or microorganisms -Infect plants

What are viroids and what do they infect?

SARS (severe acute respiratory syndrome) -it is enveloped

What disease is associated with coronaviruses?

Antigenic shift: -influenza viruses -Segments from the RNA genome from two genetically distinct strains of virus infecting the same cell are reasserted (rearrange RNA which causes mutations and basically forms a new virus/codes for Dif proteins) -generates hybrid virions that express a unique set of surface proteins unrecognized by immune system -triggers major outbreaks bc immunity to new forms absent from population. (Flu outbreaks) Antigenic drift: -influenza -minor change -you don't see the major pandemics like you do with antigenic shift.

What is antigenic shift and drift? Which virus are they associated with and why do they occur?

Native Prion proteins: found in neurons/brains of healthy animals. Pathogenic prion proteins: cause native prion proteins to change their shape and thus function. This causes the formation of plaques which destroys the brain and makes holes in the grey matter of the brain. ex = mad cow disease

What is the difference between the native and pathogenic forms of a prion protein?

liver -causes hepatitis

What is the host cell for hepadnaviruses?

-Rhabdovirus -Bullet-shaped, enveloped, helical nucleocapsid containing several enzymes -Negative strand ssRNA (must be copied to get plus strand)

What is the shaped and name of the virus that causes rabies? What type of virus is it?

All replication occurs in the cytoplasm Facts: -Smallpox was first to be studied and have a vaccine developed (Jenner) -Among largest animal viruses known -Also includes → cowpox and vaccinia virus (used as smallpox vaccine and lab model) -Cell lyses and releases virions -Double stranded DNA about 190 kilobase pairs and 250 genes -Contains certain proteins from other viruses for use in recombinant vaccines -Elicits strong immune response, formation of lesions, skin nodules, or disseminated rash.

What is unique about the Pox viruses? What type of damage do they do to their host?

The information flow is from RNA to DNA which is known as reverse transcription. Its catalyzed by the enzyme called reverse transcriptase.

What is unusual about genetic information flow in retroviruss?

Retrovirus AIDS (breakdown of immune system)

What type of virus is HIV? What does it cause?

DNA replication occurs on both DNA template strands in the nucleus -affect your adenoids -Major group of small, naked, icosahedral, linear, double-stranded DNA viruses -Cause mild respiratory infection in humans

Where in the body do you find adenoviruses?

In general, viruses go through the following five steps in their replication cycles to produce more virions1.) 1.) Adsorption: the attachment of viruses to host cells2.) 2.)Penetration: the entry of visions (or their genome) into host cells3.) 3.)Synthesis: the synthesis of new nucleic acid molecules, capsid proteins, and other viral components within host cells while using the metabolic machinery of those cells4.) 4.)Maturation: the assembly of newly synthesized viral components into complete virions5.) 5.) release: the departure of new virions from host cells. Release generally, but not always, kills (lyses) host cells

General replication of viruses

Prion -An infectious protein whose extracellular form lacks nucleic acid -Known to cause disease in animals, such as scrapie, bovine spongiform encephalopathy/mad cow, chronic wasting disease, kuru, and Creutzfeldt-Jakob disease Viroid -Infectious RNA molecules that lack a protein component -Infect plants Virus Infect bacteria, animals, plants, etc. Prions -consist of protein but have no nucleic acid of any kind -exist in two conformations the native and pathogenic

How does a prion differ from a viroid? How does a prion differ from a virus?

Infectious PROTEINS whose extracellular form contains no nucleic acids. -Known to cause disease in animals, such as scrapie, bovine spongiform encephalopathy/mad cow, chronic wasting disease, kuru, and Creutzfeldt-Jakob disease

On what basis can prions be differentiated from all other infectious agents?