chapter 13 Flashcards
virion
single particle
viruses
more than one type of virus (HIV)
What was the first virus to be discovered?
TMV, tobacco mosaic
Characteristics of viruses
-do not divide
-can carry DNA or RNA but not both
-can perform reverse transcription
-cannot carry out metabolic pathways
mama virus and mimi virus
giant viruses
extracellular state
virion
-have a protein coat called a capsid that surrounds nucleic acid
-
nucleocapsid
combination of both capsid and nucleic acid together
intracellular state
capsid is removed and the virus exists as nucleic acid
-while in host cell, they only have a genome
Why do viruses only infect certain host cells?
due to the affinity of the viral surface and the complementary proteins on the host cell
generalists
infect many kinds of cells or many different hosts
What is the smallest virion?
bacteriophage MS2
Is a virion or bacteria bigger?
bacteria
What is the biggest animal virus?
smallpox
helical
capsid composed of capsomeres bound together in a circular fashion to form a tube around the nucleic acid
polyhedral
roughly spherical capsid
complex
many different shapes
rabies
What is replication dependent on?
the hosts organelles and enzymes
lytic replication
viral replication that results in death and lysis of the hosts
-attachment, entry, synthesis, assembly, release
lysogenic replication of bacteriophages
the infected host cell grows and reproduces normally for generations before they lyse
What are bacteriophages called in their inactive state?
prophages
lysogenic conversion
phages carry genes that alter the phenotype of a bacterium from harmless to pathogenic
Animal virus replication
same replication pathway as bacteriophages
results may vary due to the presence of an envelope, lack of cell wall
In animal virus replication, where does DNA enter?
the nucleus
In animal virus replication, where does RNA replicate?
in the cytoplasm
What are the four types of RNA viruses?
ssRNA, retroviruses, dsRNA
retroviruses
do not use genomes as mRNA,(HIV), use reverse transcriptase
latency
phase where animal viruses that remain dormant in host cells
What occurs during the penetration stage of the lytic cycle?
the phage injects its DNA into the host cell
Synthesis stage of the lytic cycle
the phage causes the host DNA to break into small pieces and then uses the host to make new copies of its DNA
Assembly stage (lytic)
the phage components are assembled into virions
Release stage (Lytic)
the virons are released to infect other cells
temperate bacteriophages
their DNA forms a circle that can replicate and be transcribed or can proceed to the lysogenic cycle after penetration
Lysogenic cycle
the phage DNA integrates within the bacterial chromosome by recombination and the inserted phage DNA is a prophage
- when the bacterium reproduces, the prophage is copied
induction
prophage is excised through the host chromosomes in a process called induction in the lysogenic cycle and after the prophage can enter the lytic cycle
Which of the following proteinaceous subunits make viral capsid?
capsomere
The enzyme lysozyme is critical for which of the stages of a bacteriophage T4 infection cycle?
entry and release
