General Virology & Tobacco Mosaic Disease

virus

smaller and simpler than eukaryotes and prokaryotes infectious particle consisting of little more than genes packaged in a protein coat cant reproduce, cant do metabolic actives outside of host virus latin root = poison obligate, intracellular parasite: can only replicate within a host cell

tobacco mosaic disease

stunts the growth of tobacco plants gives tobacco plants mottled, mosaic, coloration Adolf Mayer transmittable by rubbing bad to good particle that causes = tobacco mosaic virus TMV

structure of viruses viruses [] consisting of [] enclosed by [___]

Answer: infectious particle; one or more nucleic acid; protein coat and for some membranous envelope

Genomes and Capsids

virus genome

can be double stranded dna (norm), single stranded dna, double strand rna, or single strand rna depending on virus

capsid

protein shell enclosing the viral genome rod-shaped, polyhedral, or more complex helical viruses icosahedral viruses built from capsomeres

helical

rod-shaped viruses, eg TMV rod shaped made of protein arranged in helix

icosahedral viruses

polyhedral capsid that has 20 triangular facets

capsomeres

proteins that make up capsids, many of them make up capsids

bacteriophages

most complex capsid Infect e. coli 7 types

viral envelopes

derived from membranes of host cell contain host cell phospholipids and membrane proteins contain proteins + glycoproteins of viral origin an accessory structure that helps viruses infect hosts

Viral Replication & Phages

host range

viruses can only infect a limited number of host species. name of the range

the lytic cycle

the pages replicative cycle that culminates in death of the host cell lyric = last stage of infection, when bacterium LYSES (breaks open) phages released that were produced within cell then phages can infect a healthy cell so a bacteria population can be destroyed a phage that only replicates in this cycle is virulent

virulent phage

T4, a phage that replicates only by a lytic cycle

lysogeny

state when phages [___] with host cells, prophages can generate active phages that lyse cells Answer: COEXIST

the lysogenic cycle

allows replication of phage w/o killing host temperate phages

temperate phages

lambda, phage that can go through both lysogenic and lytic cycles to replicate

prophage

viral DNA integrated into the host cell's chromosome, lysogenic cycle

Bacterial Defenses

bacterial defenses

natural selection favors bacteria w/ surface protein no longer recognized as receptor by particular phage when phage dna enters cell, foreign, so restriction enzyme cuts up

restriction enzyme

cellular enzyme that restricts phage ability to replicate in bacterium

bacterium dna

bacterium dna is methylated so that restriction enzyme doesnt attack own dna

palindrome

dna sequence reading same backwards and forwards

crispr

clustered regularly interspaced short palindromic repeats associated w/ a phage that had infected cell

cas

crispr-associate proteins, identify and cut phage dna (defending cell from phage); uses portion of phage related rna to identify invading phage dna and cut it

Animal Viruses & Retroviruses

viral envelopes

virus uses envelope to enter host cell

replicative cycle of rna genome virus

glycoproteins on viral envelope bind to receptor molecules on host cell capsid and viral genome enter cell capsid digested by cellular enzyme, viral genome released viral genome functions as template for synthesis of complementary RNA by viral RNA polymerase copies of rna are made using complementary rna strands; complementary rna also mrna, so complementary rna translated to capsid proteins + glycoproteins for viral envelope (in ER and Golgi apparatus) vesicles transport envelope glycoproteins to plasma membrane capsid assembles around viral genome molecule new virus buds from the cell, envelope studded with glycoproteins embedded in membrane (from host cell)

herpesvirus

envelope not derived from plasma membrane temporary cloacked in nuclear envelope derived envelope then shed and new golgi apparatus envelope double stranded dna genome that replicate in host dna

retroviruses

RNA animal viruses with the most complicated replicative cycles retroviruses have an enzyme called [___] that transcribes and RNA remplace into a dna copy Answer: reverse transcriptase

HIV

human immunodeficiency virus, causes AIDS

AIDS

acquired immunodeficiency syndrome, caused by HIV virus

HIV cycle

1.) enters host cell 2.) reverse transcriptase molecules released into cytoplasm 3.) dna is made 4.) new DNA enters cell nucleus 5.) dna integrates into dna of a chromosome 6.) rna polymerase makes viral rna from this viral dna and viral proteins, new viruses released from cell

provirus

integrated viral dna that never leaves the host genome, permanent resident of the cell

Evolution & Medical Treatments

evolution of viruses

possible original source of viral genomes plasmids and transposons

plasmid

small circular dna molecules found in bacteria and unicellular fungi called yeasts; exist apart from genome, replicate independently of genome. occasionally transferred between cells

transposons

dna segments that can move from one location to another withing a cell's genome

mobile genetic element

feature describing plasmids, transposons, and viruses

vaccine

harmless derivative of a pathogen stimulating the immune system to mount defenses against harmful pathogen, taken BEFORE virus affects

antibiotics

help us recover from bacterial infection, powerless against virus, they kill bacteria by inhibiting enzymes specific to bacteria but have little or no effect on eukaryotic/viral encoded enzymes

acyclovir

impeded herpes virus replication; inhibits the viral polyamerase duplicating viral dna but not eukaryotic one

azydothymidine (AZT)

curbs HIV replication, interfering with reverse transcriptase

maraviroc

blocks protein on human immune cell binding to HIV virus

Emerging Viruses & Plants

emerging virus

viruses suddenly become apparent (e.g. HIV)

epidemic

a widespread outbreak (e.g. ebola, an emerging virus causing hemorragic fever; zika; chikungunya); occur when genetic changes allow a new viral strain to be easily transmitted between humans

pandemic

a global epidemic

recombination in spread

how can recombination cause viruses to spread rapidly? for example, in pigs. h1n1 rna strands are made up of 9 rna segments, which can mix and match, reassort, during ciral assembly, creating multiple genetic variations and combinations. when they reassort, they might acquire the ability to spread to humans

horizontal transmission

an external source infects the plant. invading virus must get past epidermis of plant, plant becomes susceptible if external injury

vertical transmission

plant inherits from parent

plasmodesmata

the cytoplasmic connections that penetrate the walls between adjacent plant cells

Prions

prions

infectious proteins, cause degenerative brain diseases in animal species misfolded form of a protein normally in brain cells scrapie in sheep, mad cow diseasem jakob disease in humans transmitted in food (mad cow disease, cannibalism of a prion host) long incubation (long time to show up) molecular basis, gets into cell containing normal form of protein, misfolds normal protein into prion alzheimers and parkinsons involvement