MICROM Lecture 11 chapter 13 (Viruses, Viroids, Prions)
replicases are ____ polymerases
RNA-dependent RNA
aattachment
binding of a bacteriophage surface pritein to a host cell receptor
the number of phage particles released from a host cell is called the ____ size
burst
doublestranded genome
consists of both (+) and (-) strand
which diseases are caused by prions?
creutsfeldt-jakob disease bovine spongiform encephalopathy scrapie
after a virus gains entry to an animal cell by fusion, the virus envelope fuses with the ________
cytoplasmic membrane
integrase
directs the incorporation of phage DNA into a bacterial chromosome
benign tumor
does not spread to nearby cells
the phospholipid bilayer found surrounding the capsid of some viruses is the ______
envelope
reverse transcriptase
enxyme that uses an RNA molecule as a template to make a complementary copy of DNA
LYsogens are more susceptible to reinfection by the same type of phage
false
animal viruses can be studied by infecting ___
fertilized chicken eggs live animals cell or tissue culture
Methods by which an enveloped virus can gain entry into animal cells
fusion of the viral envelope and the cell membrane endocytosis of the virus by the host cell
the protein receptor molecules on a host cell to which viruses attach by their spikes are typically ____
glycoproteins
consequences of lysogeny include
immunity to superinfection lysogenic conversion
(-) strand genome
is the complement to mRNA
____ infections have periods of no symptoms
latent
a _______ infection results in the integration of bacteriophage DNA into the chromosome of the bacterial host
lysogenic
some pathogenic bacteria produce toxins that are incoded on prophage DNA, these are examples of ______ conversion
lysogenic
infection of bacteria by ____ phages always ends with lysis of the host cell
lytic
Productive Infection
new viral particles are produced
most animal DNA viruses replicate within the host cell's ____
nucleus
viruses are classified as ______ because they are dependent on host cells
obligate intracellular parasites
endocytosis
only way for animal virus to enter a host cell that does not have an envelope
repressor protein
prevents expression of the gene required for excision to maintain the lysogenic state
RNA viruses have a higher mutation rate than DNA viruses because replicase lacks ______ ability
proofreading
capsid
protein cell that protects viral genome from the environment
specialized transduction
result of excision errors made as temperate phages transition from a lysogenic to a lytic cycle
Specilized transduction
results in errors in excision of the prophage produces defective phaage particles tansfers phage DNA and adjacent host genes
(+) strand genome
serves as mRNA
Which facts best supports the position that viruses are not living organisms?
1. Viruses cannot reproduce on their own 2. Viruses are intert outside of a host
Occur during sythesis stage of the T4 lytic cycle
Degradation of bacterial DNA synthesis of phage proteins synthesis of phage DNA
a consequence of lysogeny that could result in human disease
Lysogenic conversion
two major categories of viral infections
acute persistent
When two different strians of a segmented virus enter the same cell, reassortment of the gene segments can occur, resulting in
antigenic shift
generalized transduction
any bacterial gene can be transferred
the _____ or maturation stage of the T4 phage lytic cycle is marked by the formatino of new phage particles inside of the host cell
assembly
steps of an animal virus infection cycle
attachment Penetration and uncoating synthesis of viral proteins and replications of the genome assembly release
Many animal viruses have proteins called _____ that attach to receptors on a host cell
spikes
milgnant tumor
spreads to nearby cells
lysis
term used to describe the rupture or bursting of a cell
enveloped viruses can derive their envelopes from _____
the host cytoplasmic membrane certain host organelles
the study of viruses is important beause ____
there are many medically important viruses that cause disease bacteriophages play a significant ecological role in reducing bacterial populations in nature viruses can be a behicle for horizontal gene transfer in bacteria
processes required for production of virus particles in a host cell
transcription of viral genes replication of viral genome translation of viral genes
bacteriophaes play a fundamental role in which type of horizontal gene transfer?
transduction
Specilized transduction____
transfers phage DNA and (ONLY ) adjacent host genes produces defective phage particles results from errors in excision of the prophage
mechanisms newly assembled viruses use to leave their host cell
triggering apoptosis budding
after a virus enters a cell, the nucleic acid separates from the protei coat, a process called _____
uncoating
latent state
viral genome remains silent within cell
retrovirus
virus that uses reverse transcriptase to make a DNA copy from its RNA genome; HIV
bacteriophages; phages
viruses that infect bacteria
animal viruses
viruses use their spikes to attach to host cell receptors some viruses require more than one host receptor for attachment blocking a ost receptor with a drug would prevent a virus from infecting that cell