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