Ch 10 microbio

RNA viruses

must carry the RNA dependent RNA polymerase needed for replication and transcription of their genome in their nucleocapsid Cellular organism do not possess these enzymes

Lipid bilayer

not encoded by the virus but stolen from the host cell lipid bilayer during infection process

Complex

possess either helical or icosahedral, both, or different capsid structures

Encephalomyocarditis virus is a member of the Picornaviridae (same virus family as Poliovirus) that primarily affects piglets. It causes both encephalitis (inflammation of the brain) and myocarditis (inflammation of the heart muscle) and is usually fatal. Since this is a Group IV virus, how would it replicate?

+ssRNA --> -ssRNA --> +ssRNA

Group 1

double-stranded DNA genomes, that are transcribed directly into mRNA by a DNA-dependent RNA polymerase

Naked viruses usually exit host cells by budding. T/F

False

Three nucleocapsid symmetries

Helical, icosahedral or complex

Attachment

viruses attach host cells through interaction of viral ligands with specific host receptors

Why aren't viruses found in the three systems of life

1) acellular 2)Viruses do not code for their own ribosomes and cannot carry out protein synthesis on their own 3)viruses are not capable of making their own ATP

Influenza virus is an atypical Group V virus. Influenza virus replication occurs in the nucleus, rather than in the cytoplasm (like other Group V viruses). They also differ from Group IV viruses in a rather significant way. Which of these reasons explain(s) the difference between Influenza virus and Encephalomyocarditis virus? a)Influenza requires a different polymerase than Encephalomyocarditis virus b)Influenza uses host translational machinery, while Encephalomyocarditis doesn't c)Influenza genome is not the same sense as mRNA, while Encephalomyocarditis i d)Influenza does not need mRNA, while Encephalomyocarditis does e)Influenza does not require a template strand, while Encephalomyocarditis does

C

Enveloped virus

possess an additional lipid bilayer must possess embedded proteins in their lipid bilayer embedded proteins: glycoprotein spikes

Helical

promoters arranged in helical fashion around the nucleic acid

Rotavirus is a common causative agent of gastroenteritis (stomach and intestinal inflammation). It is especially common among infants and young children, and can be fatal, due to severe dehydration brought on by excessive watery diarrhea. Rotavirus is a Group III virus, and therefore it requires a(n) ___________ encoded by the _________to be able to replicate.

RNA-dependent RNA polymerase, virus

Nucleocapsid

formed by the nucleic acid and protein coat

Group 7

gapped, double-stranded DNA viruses. Their transcription involves repair of the gapped dsDNA genome by DNA-dependent DNA polymerase, succeeded by transcription with DdRP.

What does the baltimore system allow for

good deal of information to be inferred from the genome structure alone

Attachment to host cells occurs when viral ________ bind to host cell ____________

ligands, receptors

Entry of viruses into animal cells is either the result of _______ or ________

membrane fusion, receptor mediated endocytosis

Exit

naked viruses exit through lysis of the host cell enveloped cells exit through either budding or exocytosis

Group 4

positive-sense, single-stranded RNA which may be directly translated (+ssRNA=mRNA) or will be converted to negative-sense, single-stranded RNA and then back to +ssRNA by a viral RdRP.

Group 6

possess +ssRNA genomes, but create a double-stranded DNA intermediate before transcription occurs. This is mediated by RNA-dependent DNA polymerases (RdDP or reverse transcriptase) and is necessary because these viruses are known to integrate into the host double-stranded DNA chromosome.

Assembly

result of self assembly or viral direction of host machinery to assemble to mature virions Capsid proteins are recruited to polymerize around viral genome copies to yield mature nucleocapsid along with any genome associated proteins or enzymes

Group 5

reverse of group IV viruses and possess negative-sense, single-stranded RNA genomes that are transcribed to mRNA by the viral RdRP.

Group 2

single-stranded DNA genome first made into a double-stranded DNA intermediate by a DNA-dependent DNA polymerase (DdDP), and then transcribed into mRNA by a DdRP.

Adeno-associated virus (AAV's) belongs to a group of viruses that are being used in clinical trials for targeted gene therapy in a variety of conditions including congestive heart failure, hemophilia, and cystic fibrosis. The use of AAV's is very effective because they are Group II viruses. This means that they have a ____________ genome.

ss DNA

Why do many viruses encode and produce replicase and/or transcriptase

to make more copies of their genome or to express viral genes inside the hose cell

Entry

viral entry into host cells occur differently for bacteriophage than animal viruses. Following attachment, bacteriophages expel their nucleic acid genome into the cytoplasm of the host cells Typically involves enzymatic activity and/or exertion of mechanical force to penetrate the cell wall and membrane of bacterial cells

lysis

result of action of viral proteins

What are viral genomes protected from the environment by?

A capsid composed of virus encoded proteins

Viruses may be "naked" like Tobacco Mosaic Virus (TMV) or enveloped in a lipid bilayer like Influenza virus. Which statement best characterizes enveloped viruses? a)The envelope is derived from the host cell b)The envelope is coded for by the viral genome c)The envelope is synthesized by the virus while it is waiting to find a new host d)The envelope contains only host proteins and none of viral origin e)The envelope is a not a phospholipid bilayer

A

Viruses are not included in the three domain system of life. What is/are characteristic(s) of viruses? a)Viruses are capable of replicating on their own, without a host cell b)Viruses are acellular c)Viral genomes are always DNA d)Viruses are generally larger than bacteria e)Viruses make their own ATP

B

Group VI viruses are called retroviruses and include the Human Immunodeficiency Virus. They have a unique replication cycle involving an RNA-dependent DNA polymerase. For what reason do retroviruses use an RNA-dependent DNA polymerase? a)Replication of the viral genome for packaging into new virions b)Transcription of the viral genome for future translation c)Conversion of the viral genome into the same nucleic acid as the host d)Conversion of the host genome into the same nucleic acid as the virus e)Degradation of host nucleic acids

C

Human papillomavirus (HPV) is the causative agent of genital warts and is the most common sexually transmitted infection (STI) in the United States. HPV has a relatively small double-stranded DNA genome (Group I Virus) that codes for 8 proteins. Given this information, what do you know about HPV? a)HPV must encode its own DNA-dependent DNA polymerase b)HPV uses the host DNA-dependent RNA polymerase c)HPV uses the host translational machinery d)Both B and C e)All of the above

D

Baltimore system

Divides viruses into seven distinct groups based on their nucleic acid genome and their method of producing RNA

Group VII viruses include the Hepadnaviridae (hepatitis viruses). These viruses cause inflammation of the liver (hepatitis), that can often be fatal (especially if untreated). The hepatitis viruses require several different enzymes to complete their rather unorthodox life cycle. Which of the enzymes below might be involved in the INITIAL step that converts the gapped dsDNA viral genome into intact dsDNA? a)DNA ligase b)Reverse transcriptase c)DNA-dependent DNA polymerase d)Both A and B e)Both A and C

E

Which of the following things must happen during the biosynthesis phase of the viral life cycle? a)Replication of the viral genome b)Translation of viral proteins c)Transcription of the viral genome d)Hijacking of host cellular machinery e)All of the above

E

What do all virions possess

a nucleic acid genome surrounded by a protein coat

Budding

acquire lipid bilayer from a process that is essentially the reverse of membrane fusion

Icosahedral

arrangement of pentamers or hexamers to form an icosahedron that encapsulates the nucleic acid genome

Five steps of virus replication

attachment/absorption, entry/penetration, biosynthesis, assembly and exit

How is biosynthesis achieved

combination of viral encoded and host encoded machinery

Goal of biosynthesis

create copies of the genome and other necessary protein components for daughter virions

Group 3

double-stranded RNA genomes that are transcribed into mRNA by RNA-dependent RNA polymerases

Matrix proteins

effective protein shells with affinity for the nucleocapsid along the interior surface and the glycoprotein spikes along their outer surface

Where are viruses that complete their life cycle by exocytosis processed?

endoplasmic reticulum or golgi apparatus

Entry of enveloped viruses

enter by membrane fusion or by receptor mediated endocytosis

Eukaryotic entry

enter host cells through membrane fusion or receptor mediated endocytosis

Naked virus

exposed nucleocapsid interact with host cells directly via capsid proteins which serve as viral ligands for host cell receptors