BISC 261 Exam Questions and answers with complete solutions Latest Updated 2025 |
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how are viruses similar to cellular organisms? - ✔️✔️Viruses replicate and can adapt to their environment,but
they lack an independent metabolism and are completely reliant on host cells to replicate
what is the difference between a nucleocapsid and a capsid? - ✔️✔️The nucleocapsid refers to the nucleicacid
and its surrounding capsid, and the capsid is the protein coat that surrounds the virions nucleic acid.
compare the structure of an icosahedral capsid with that of a helical capsid. How do pentamers and
hexamers associate for form a complete icosahedron? - ✔️✔️An icosahedral capsid is a viral capsid that has
a shape of a regular polygon with 20 equilateral triangular faces and twelve corners. Helical capsids are
viral capsids in the form of a helix, shaped like hollow tubes with protein walls
what is an envelope? What are spikes? - ✔️✔️And envelope is an outer membrane layer that surrounds the
nucleocapsid of some viruses. A peplomer I a protein complex that extends from the viral envelope and
is usually important in the virions attachment to the host cell surface
all four nucleic acid forms can serve as viral genomes. describe each. what is a segmented RNA genome?
- ✔️✔️dsDNA: double stranded dna
ssDNA: single stranded DNA
ssRNA: single stranded RNA
dsRNA: double stranded RNA
a segmented genome is a viral genome that is divided into several parts or fragments, each for coding a
single polypeptide
why do the receptors viruses have evolved host surface proteins that are important or sometimes
essential for host cell function? - ✔️✔️viruses have evolved to attach to receptors that are always presenton the
host cell
what plays the most important role in determining the tissue and host specificity of viruses? - ✔️✔️thecellular
receptors present on the host cell
, why are DNA viruses more dependednt on their host cells than RNA viruses? - ✔️✔️some dsDNA viruses depend
solely on the host cells biosynthetic machinery to replicate genomes and synthesize proteins.
lysogeny - ✔️✔️the state in which a viral genome remains within a bacterial or archaeal cell after infectionand
reproduces along with it, rather than taking control of the host cell and destroying it.
temperate phage - ✔️✔️A phage that is capable of reproducing by either the lytic or lysogenic cycle.
lysogen - ✔️✔️bacterial and archaeal cells that carry a provirus and can produce viruses under proper
conditions
prophage - ✔️✔️the form of the virus that remains inside its host
induction - ✔️✔️the events that trigger a virus to switch from a lysogenic mode to a lytic pathway
what are the beneftis of a phage being capable of lysogeny? - ✔️✔️it allows the viral nucleic acid to be
maintained within its host. in a situation where there are many more phages in an environment than
there are host cells, lysogeny allows the virus to continue using the host for reproduction when they
would otherwise be destroyed
what is lysogenic conversion and why is it important? - ✔️✔️when the temperate phage changes the
phenotype of its host
how does a latent infection differ from a chronic infection? - ✔️✔️in a latent infection, there is a viral
genome present but the host is unharmed. in a chronic infection, there is a slow release of the virus
without cell death
What is a cytocidal infection? - ✔️✔️results in cell death through lysis
What is the cytopathic effect? - ✔️✔️Observable damage to a cell resulting from virus infection
Verified
how are viruses similar to cellular organisms? - ✔️✔️Viruses replicate and can adapt to their environment,but
they lack an independent metabolism and are completely reliant on host cells to replicate
what is the difference between a nucleocapsid and a capsid? - ✔️✔️The nucleocapsid refers to the nucleicacid
and its surrounding capsid, and the capsid is the protein coat that surrounds the virions nucleic acid.
compare the structure of an icosahedral capsid with that of a helical capsid. How do pentamers and
hexamers associate for form a complete icosahedron? - ✔️✔️An icosahedral capsid is a viral capsid that has
a shape of a regular polygon with 20 equilateral triangular faces and twelve corners. Helical capsids are
viral capsids in the form of a helix, shaped like hollow tubes with protein walls
what is an envelope? What are spikes? - ✔️✔️And envelope is an outer membrane layer that surrounds the
nucleocapsid of some viruses. A peplomer I a protein complex that extends from the viral envelope and
is usually important in the virions attachment to the host cell surface
all four nucleic acid forms can serve as viral genomes. describe each. what is a segmented RNA genome?
- ✔️✔️dsDNA: double stranded dna
ssDNA: single stranded DNA
ssRNA: single stranded RNA
dsRNA: double stranded RNA
a segmented genome is a viral genome that is divided into several parts or fragments, each for coding a
single polypeptide
why do the receptors viruses have evolved host surface proteins that are important or sometimes
essential for host cell function? - ✔️✔️viruses have evolved to attach to receptors that are always presenton the
host cell
what plays the most important role in determining the tissue and host specificity of viruses? - ✔️✔️thecellular
receptors present on the host cell
, why are DNA viruses more dependednt on their host cells than RNA viruses? - ✔️✔️some dsDNA viruses depend
solely on the host cells biosynthetic machinery to replicate genomes and synthesize proteins.
lysogeny - ✔️✔️the state in which a viral genome remains within a bacterial or archaeal cell after infectionand
reproduces along with it, rather than taking control of the host cell and destroying it.
temperate phage - ✔️✔️A phage that is capable of reproducing by either the lytic or lysogenic cycle.
lysogen - ✔️✔️bacterial and archaeal cells that carry a provirus and can produce viruses under proper
conditions
prophage - ✔️✔️the form of the virus that remains inside its host
induction - ✔️✔️the events that trigger a virus to switch from a lysogenic mode to a lytic pathway
what are the beneftis of a phage being capable of lysogeny? - ✔️✔️it allows the viral nucleic acid to be
maintained within its host. in a situation where there are many more phages in an environment than
there are host cells, lysogeny allows the virus to continue using the host for reproduction when they
would otherwise be destroyed
what is lysogenic conversion and why is it important? - ✔️✔️when the temperate phage changes the
phenotype of its host
how does a latent infection differ from a chronic infection? - ✔️✔️in a latent infection, there is a viral
genome present but the host is unharmed. in a chronic infection, there is a slow release of the virus
without cell death
What is a cytocidal infection? - ✔️✔️results in cell death through lysis
What is the cytopathic effect? - ✔️✔️Observable damage to a cell resulting from virus infection
