Ch 19 Viruses Flashcards

40438897	size of viruses	20 nm diameter, smaller than ribosome
40438898	virus genome	double or single stranded DNA or RNA (NOT both)
40438899	capsid	protein shell enclosing the viral genome
40438900	virus genome organization	usually a single linear or circular molecule of nucleic acid, sometimes multiple molecules of nucleic acid
40438901	capsid subunits	protein subunits called capsomeres
40438902	Viral envelope	some viruses have them, membrane made from the host cell's plasma membrane, helps virus infect host
40438903	Viral envelops contain	host cell phospolipids and membrane protein, proteins and glycoproteins of viral origin
40438904	bacteriophages	also called phages, viruses that infect bacteria
40438905	host range	specific type of cell, tissue, species, or range of species that a virus can intect
40438906	Viruses identify host cells by	"lock and key" fit between viral surface proteins and specific receptor molecules outside the cells
40438907	How viruses reproduce	use their nucleic acid to code for some proteins and enzymes, but uses the cell's other resources
40439913	DNA viruses use	DNA polymerase of the host cell to synthesize new genomes
40439914	RNA viruses use	virally encoded polymerases that can use RNA as a template
40439915	lytic cycle of phages	stage of infection during which the bacteria lyses and releases the phages that were produced within the cell
40439916	virulent phage	reproduces only by a lytic cycle
40439917	Bacteria and natural selection	natural selection faocrs bacterial mutants with receptors that are no longer recognized by phages
40439918	restriction enzymes	enzymes that cut up foreign DNA when phage DNA enters a bacterium
40439919	DNA protects itself from its own restriction enzymes by	DNA methylation
40439920	lysogenic cycle	allows replication of the phage genome without destroying the host
40439921	temperate phages	capable of using the lytic and lysogenic cycle
40439922	temperate phage in research	lambda
40439923	prophage	viral DNA that has integrated into the bacterial chromosome
40439924	triggers switchover from lysogenic to lytic mode	an environmental signal, such as a certain chemical or high-energy radiation
40439925	prophage genes expressed during lysogeny	gene for a prophage transcription-preventing protein, and others
40439926	expression of lysogenic genes	may alter the host's phenotype, a phenomenon important for medical significance
40439927	stages of the lytic cycle	attachment, entry of phage DNA and degradation of host DNA, synthesis of viral genomes and proteins, assembly, and release (lysozyme is produced, host cell wall and membrane our lysed)
40439928	phage assembly	head, tail, and tail fibers
40439929	stages of lysogenic cycle	phage DNA integration into bacterial DNA, bacterium reproduction, occasionally heads to lytic cycle
40440581	animal virus envelopes	many have glycoprotein projections, virus wraps host cell membrane around them to form the envelope
40440582	retrovirus	RNA as genetic material, use reverse transcriptase enzyme to produce DNA, then uses transcription and translation to reproduce. example is HIV
40440583	bacteriophages rarely	have an envelope or RNA genome, but animals often have both
40440584	provirus	integrated viral DNA, permanent resident of the cell
40440585	vesicles transport	envelope glycoproteins to the plasma membrane
40440586	proviral genes are transcribed	into RNA molecules, genomes for the next viral generation and as mRNAs for translation
40440587	viral proteins include	capsid proteins and reverse transcriptase (made in cytosol) and envelope glycoproteins (made in the ER)
40440588	Plasmids	small, circular DNA molecules found in bacteria and yeasts, exist apart form the cell's genome but can replicate independently of it and are occasionally transferred
40440589	Transposons	DNA segments that can move from one location to another within the cell's genome
40440590	mobile genetic elements	plasmids, transposons, and viruses
40440591	viruses originated from	probably evolved after life appeared from naked bits of cellular nucleic acids that moved from one cell to another, perhaps via cell surfaces
40440592	vaccine	harmless variant or derivative of a pathogen that stimulates the immune system to mount defenses against the harmful pathogen
40440593	anti-viral drugs	try to interfere with viral replication, antibiotics do not work
40440594	emerging viruses	appear suddenly or are new to medical scientists (example sars)
40440595	epidemics	general outbreaks of a viral disease
40440596	most antiviral drugs resemble	a nucleoside, as a result interfere with viral nucleic acid synthesis
40440597	causes of emerging viruses	mutation of existing viruses, spread of the virus from one host to another, and global travel and spread of virus within a host group
40440598	RNA virus high rate of mutation because	RNA genomes not corrected by proofreading
40440599	pandemic	global epidemic
40440600	viral genomes and proteins spread through a plant by	plasmodesmata, the cytoplasmic connections that penetrate the walls between adjacent plant cells, virally encoded proteins enlarge the plasmodesmata
40440601	viroids	circular RNA molecules, only a few hundred nucleotides long, that infect plants
40440602	viroid function	do NOT encode proteins, but can replicate in host plant cells and use host cell enzymes, cause errors in the regulatory systems that control plant growth
40440603	prions	infectious proteins which appear to cause a number of degenerative disease in various animal species
40440604	prion characteristics	act very slowly and are virtually indestructible
40440605	prion infects other proteins by	somehow converting normal protein molecules into misfolded prion versions, example mad cow disease