Ch.13 Flashcards
What makes a virus a virus?
protein + nucleic acid at minimum. Not cell based, and either DNA or RNA never both.
What makes a viroid?
just nucleic acids
What is a prion made of
Proteins, abnormal prions are the problem
Why aren’t viruses living?
They obligatory intracellular parasites, they ONLY reproduce inside other cells. No atp generating mechanisms no ribosomes
Tissue Tropism
when viruses only infect specific types of cells in one host
Host range
range of viable infection, determined by specific host attachment sites and cell factors
What do you see viruses with
Electron microscope, they are smaller than RBC and bacteria. They are tiny
What is the protein coat on a virus called and what does it do
A capsid and protects the nucleic acid of a virus. Sometime it is covered in an envelope made of lipids made from the host cell. Capsomeres are the proteins that make up the capsid. Sometimes the capsid have spikes that allow it to attach to a host, they made of carbohydrates and proteins
What are the virus shapes?
Helical, polyhedral, enveloped, and complex viruses.
Helical Virus
Looks like a rod or cylinder. Including the capsid. Like rabies and ebola.
Polyhedral Virus
20 triangular faces with 12 corners , a polyhedron called a icosahedron. like the polio virus.
Enveloped virus
roughly spherical, we call enveloped shapes enveloped helical or enveloped polyhedral.
Complex Viruses
can have a polyhedral head and helical body, capsid may allow attachment for more stuff . Like bacteriophage.
how are viruses taxoiminzed?
family name ends in viridae , A viral species shares and their ecological niche (host) genetic info and characteristics. common names are used for species, subspecies are designed by number.
What is the family, genus, and subspecies of herpes?
Family- Herpes viridae, genus- herpesvirus sub- HHV-1, HHV-2
Bacteriophages
viruses that kill bacteria, they form plaques or patches of plaques
how are viruses grown?
must be grown in living animals or embryonic eggs (for animal virusus). Living cells.
Lytic cycle
one of two cycle of virus reproduction. 1. T- Even Phage attaches to host cell. 2. penetration and inject DNA, 3. biosynthesis of viral components. 4.Maturation of viral components 5. release of new virions. Ends in lysis of cell
What are cytopathic effects
the degrative/pathologic effects that viruses have on cells, we can observe them to help us identify what virus they are.
Describe the lytic cycle in the one step growth curve
- eclipse period is biosynthesis then peaks at acute infection, when they are released.
Describe transduction by bacteriophage
during the biosynthesis phase, sometimes pieces of bacterial DNA is caught in the phage capsid, then when that virus goes to another cell, it can cause recombination and give them new cell some new DNA . They do not give the phage DNA
Lysogenic cycle
aka lambda phage cycle , is when the lytic cycle can result in giving a host new DNA , it is now Prophage DNA
how do animal viruses replicate? Differences with the lytic cycle
Penetration can be done by fusion, the lipid envelope melts into the lipid membrane or endocytosis where the entire thing goes in . After penetration the virus uncoats, and the protein coat leaves to release the enzymes and nucleic acids. Then on release it can leave by budding or lysis.
What is specialized transduction
Where an already prophage infected cell exercises it genome to separate but it takes some of it hosts DNA. When it the lytic cycle occurs the new phage has part of its DNA and injects it into the new cell.
RNA viruses with ssRNA
+ sense strand acts as mRNA and makes proteins directly can make RNA dependent RNA polymerase.
Retroviruses
RNA–> DNA –> RNA –> Protein
Where do DNA and RNA viruses replicate?
DNA viruses replicates in the nucleus
RNA replicated in the cytoplasms
Oncogenes
activation of these cause normal cells to turn into cancer cells
Transformed cells
the tumor cells pick up traits they wouldn’t normally have, and also have a virus specific antigen on their cell surface called tumor-specific transplantation antigen in their nucleas called a T antigen
Viruses that cause cancer
Oncogenic DNA and RNA viruses
How do viruses cause cancer
Activation of oncogenes or disrupting tumor suppressant genes
Latent Virus
remains in asymptomatic host for long periods then appears suddenly
Persistent virus
generally fatal and builds up over time, like measles
Persistent virus
generally fatal and builds up over time, like measles, acute infection quickly builds up and goes down.
Oncogenic DNA viruses
Adenoviridae, Herpes, Pox, Papo, Hepa
oncogenic RNA viruses
retro, HTLV1, HTLV2
What are prions
Protein, tramission via eating , transplant, and surgical instruments , mad cow, fatal familia insomia, creutzfeldt-jakob disease
Normal cellular prion protein on cell surface
PrP^c
Scrapie protein accumulates in brain cells and forms plaque
PrP^sc can infect normal proteins too.
Plant Viruses
enter via plant wound or insect
Viroid’s
infections RNA that hurt plants , they may interrupt chromosomes or kill mRNA
Adenoviridae
Double stranded DNA , nonenveloped, causes reparatory problems in humans and tumors in animals
Papovaviridae
Double stranded DNA nonenveloped , separated into two families. Papillomavirus the human wart virus that can cause cancer and the polyomavirus that causes tumors , some cause cancer
Poxviridae
Double stranded DNA enveloped virus causes small pox and orthopox virus, and any pox virus
Herpesviridae
Double stranded DNA, enveloped viruses causes a vareity of disease and can be latent in many hosts simplexvirus
Hepadnaviridae
Double stranded DNA enveloped . Hepatitis B
Picornaviridae
nonenveloped single stranded RNA Hepatitis A, rhinovirus and poliovirus
Flavivirdae
enveloped Single stranded RNA + strand Hepatitis C
Coronaviridae
enveloped single stranded RNA + , causes upper respiratory infections like SARS and covid 19
Rhabdoviridae
Eveloped single stranded RNA - causes numerous animal diseases like vesiculovirus and lyssavirus
Filoviridae
Single stranded RNA , - strand enveloped helico virus like ebola
