MIBO 3500 Exam 3 UPDATED ACTUAL
Exam Questions and CORRECT Answers
Dmitri Ivanovsky - CORRECT ANSWER✔✔- -studied Tobacco Mosaic Disease to find a
bacterial cause for it
-saw that bacterial agent was not removed by bacterial filters
-mottling of leaves, stunted leaves, wrinkles
Beijerinck - CORRECT ANSWER✔✔- -studied Tobacco Mosaic Disease and also saw that
the agent was not removed by bacterial filters
-coined the term "virus" for something so small that it must pass through the filters
Loeffler & Frosch - CORRECT ANSWER✔✔- -former Koch students
-studied infectious Foot & Mouth Disease of Livestock (causes high fever, blisters, weight
loss)
-agent not removed by bacterial filter
-thought agent was chemical or protein
Peyton Rous - CORRECT ANSWER✔✔- -studied sarcomas in chickens
-cell-free filtrate from diseased chickens transmitted tumors to healthy chickens
-cancer transmitted by a virus
Viruses - CORRECT ANSWER✔✔- -only a few beneficial viruses
-exceptions: viruses that kill pathogens or gene therapy usage
Most viruses cause harm. What are the few exceptions to this? - CORRECT ANSWER✔✔-
viruses that kill pathogens or viruses that are used for gene therapy
Characteristics of Viruses - CORRECT ANSWER✔✔- -at most one molecule of DNA or
RNA enclosed in a coat of protein
-obligate parasites; may have additional layers;
,-cannot reproduce independent of living cells nor carry out cell division
-can exist extracellularly
Virus Classification - CORRECT ANSWER✔✔- grouped by shared characteristics: nature of
nucleic acid, symmetry of protein shell, presence or absence of a lipid membrane, nucleic
acid comparisons
Virus Structure - CORRECT ANSWER✔✔- virion size range is ~10 - 1000 nm in diameter
- contains a nucleocapsid: nucleic acid (DNA or RNA), and protein coat (capsid)
- some have additional components
brightfield microscopes lack resolving power to find virus, but electron microscopes can
Nucleocapsid - CORRECT ANSWER✔✔- (Virus) composed of nucleic acid (DNA or RNA)
and a protein coat (capsid)
Envelopes - CORRECT ANSWER✔✔- (Virus) plasma membrane components derived from
their host (virus called naked if it does not have one)
Spikes - CORRECT ANSWER✔✔- (Virus) proteins used for attachment to host
Capsids - CORRECT ANSWER✔✔- (Virus) protect viral genetic material & aids in its
transfer between host cells; made of protein units called protomers --> capsomers
Capsomers - CORRECT ANSWER✔✔- (Virus) protomers aggregate to form this
Possible shapes of capsids - CORRECT ANSWER✔✔- helical, icosahedral, or complex
Helical/filament Capsids - CORRECT ANSWER✔✔- (Virus) shaped like hollow tubes with
protein walls; may be bent or twisted
, Icosahedral Capsids - CORRECT ANSWER✔✔- polyhedral with 20 identical triangular
faces; structure exhibits rotational symmetry (adenovirus)
Complex capsids - CORRECT ANSWER✔✔- mix of both helical and icosahedral
Types of Genomes that Viruses Can Have - CORRECT ANSWER✔✔- double-stranded
DNA, single-stranded DNA (+/sense),
single-stranded RNA (+/sense), single-stranded RNA (-/antisense), double-stranded RNA
Virus Replication Stages - CORRECT ANSWER✔✔- Host Recognition & Attachment
Genome Entry
Assembly of Virions
Exit & Transmission
Cell-surface receptors - CORRECT ANSWER✔✔- -contact and attachment of
bacteriophages to bacteria are mediated by these
-proteins that are specific to the host species
-normally used for important functions for host cell (constantly expressed)
"Ghost" capsid - CORRECT ANSWER✔✔- when the phage's capsid remains outside
attached to the cell surface after the genome has been inserted into the cell
ie. Phage T4 DNA insertion
Lytic cycle - CORRECT ANSWER✔✔- bacteriophage quickly replicates, killing host cell
Lytic cycle steps - CORRECT ANSWER✔✔- 1. Virus attaches to host cell via surface cell
receptors
2. Phage injects double-stranded DNA into the host
3. Host cell makes viral genomes and proteins
Exam Questions and CORRECT Answers
Dmitri Ivanovsky - CORRECT ANSWER✔✔- -studied Tobacco Mosaic Disease to find a
bacterial cause for it
-saw that bacterial agent was not removed by bacterial filters
-mottling of leaves, stunted leaves, wrinkles
Beijerinck - CORRECT ANSWER✔✔- -studied Tobacco Mosaic Disease and also saw that
the agent was not removed by bacterial filters
-coined the term "virus" for something so small that it must pass through the filters
Loeffler & Frosch - CORRECT ANSWER✔✔- -former Koch students
-studied infectious Foot & Mouth Disease of Livestock (causes high fever, blisters, weight
loss)
-agent not removed by bacterial filter
-thought agent was chemical or protein
Peyton Rous - CORRECT ANSWER✔✔- -studied sarcomas in chickens
-cell-free filtrate from diseased chickens transmitted tumors to healthy chickens
-cancer transmitted by a virus
Viruses - CORRECT ANSWER✔✔- -only a few beneficial viruses
-exceptions: viruses that kill pathogens or gene therapy usage
Most viruses cause harm. What are the few exceptions to this? - CORRECT ANSWER✔✔-
viruses that kill pathogens or viruses that are used for gene therapy
Characteristics of Viruses - CORRECT ANSWER✔✔- -at most one molecule of DNA or
RNA enclosed in a coat of protein
-obligate parasites; may have additional layers;
,-cannot reproduce independent of living cells nor carry out cell division
-can exist extracellularly
Virus Classification - CORRECT ANSWER✔✔- grouped by shared characteristics: nature of
nucleic acid, symmetry of protein shell, presence or absence of a lipid membrane, nucleic
acid comparisons
Virus Structure - CORRECT ANSWER✔✔- virion size range is ~10 - 1000 nm in diameter
- contains a nucleocapsid: nucleic acid (DNA or RNA), and protein coat (capsid)
- some have additional components
brightfield microscopes lack resolving power to find virus, but electron microscopes can
Nucleocapsid - CORRECT ANSWER✔✔- (Virus) composed of nucleic acid (DNA or RNA)
and a protein coat (capsid)
Envelopes - CORRECT ANSWER✔✔- (Virus) plasma membrane components derived from
their host (virus called naked if it does not have one)
Spikes - CORRECT ANSWER✔✔- (Virus) proteins used for attachment to host
Capsids - CORRECT ANSWER✔✔- (Virus) protect viral genetic material & aids in its
transfer between host cells; made of protein units called protomers --> capsomers
Capsomers - CORRECT ANSWER✔✔- (Virus) protomers aggregate to form this
Possible shapes of capsids - CORRECT ANSWER✔✔- helical, icosahedral, or complex
Helical/filament Capsids - CORRECT ANSWER✔✔- (Virus) shaped like hollow tubes with
protein walls; may be bent or twisted
, Icosahedral Capsids - CORRECT ANSWER✔✔- polyhedral with 20 identical triangular
faces; structure exhibits rotational symmetry (adenovirus)
Complex capsids - CORRECT ANSWER✔✔- mix of both helical and icosahedral
Types of Genomes that Viruses Can Have - CORRECT ANSWER✔✔- double-stranded
DNA, single-stranded DNA (+/sense),
single-stranded RNA (+/sense), single-stranded RNA (-/antisense), double-stranded RNA
Virus Replication Stages - CORRECT ANSWER✔✔- Host Recognition & Attachment
Genome Entry
Assembly of Virions
Exit & Transmission
Cell-surface receptors - CORRECT ANSWER✔✔- -contact and attachment of
bacteriophages to bacteria are mediated by these
-proteins that are specific to the host species
-normally used for important functions for host cell (constantly expressed)
"Ghost" capsid - CORRECT ANSWER✔✔- when the phage's capsid remains outside
attached to the cell surface after the genome has been inserted into the cell
ie. Phage T4 DNA insertion
Lytic cycle - CORRECT ANSWER✔✔- bacteriophage quickly replicates, killing host cell
Lytic cycle steps - CORRECT ANSWER✔✔- 1. Virus attaches to host cell via surface cell
receptors
2. Phage injects double-stranded DNA into the host
3. Host cell makes viral genomes and proteins
