MicroBiology Flashcards
B is Correct.
Any viruses that had already completed the replication process when the cyanide was added will not be affected, and will remain infectious.
If the ratio of adenine to thymine in a DNA virus is not one to one, what can be said about the genome of this virus?
Adenine base pairs with thymine in double-stranded DNA. Thus, for every A there should be one T for a one to one ratio of A to T. If the ratio differs from this, the genome must be single-stranded DNA, or RNA, which has no T.
A disease agent that is isolated from a human cannot reproduce on its own in cell-free broth but can reproduce in a culture of human cells. In its pure form it possesses both RNA and DNA. Is it possible that the disease agent is a virus?
No, it can’t be a virus. Viruses possess only one kind of nucleic acid. The disease agent is another kind of obligate intracellular parasite.
NOTE: certain bacteria like Chlamydia, can only reproduce inside host cells.
What is the likely result if a viral genome is tripled in size?
The viral genome will probably no longer fit within the normal viral structure, and the genome will therefore not be packaged into infectious viral particles.
How do ribosomes used to translate viral proteins compare to host ribosomes?
Viruses use host ribosomes. Viral and host ribosomes are translated by the same ribosomes.
C is Correct.
The only way to do this is with overlapping several frames.
Why might a bacteriophage inject its DNA, while animal viruses don’t?
a bacteriophage must puncture the cell wall, while animal viruses can be internalized whole into animal cells since animals don’t have cell walls.
All phages and plant viruses are naked viruses, meaning they don’t have envelopes. Why is this?
Viruses acquire envelopes by budding through host membranes. Phages and plant viruses infect hosts that have cell walls. When these viruses begin to exit the cell, the cell wall is destroyed and the host membrane is ruptured. Thus there is no membrane through which the remaining viruses must bud; they simply escape in lytic explosion.
If antibodies to a viral capsid protein are ineffective in blocking infection, what might this indicate about the virus?
It suggests that the virus is enveloped, so the antibody can’t reach its epitope on the capsid surface in the infectious virus.
If lysozyme of a bacteriophage were an early gene, would this be advantageous to the virus?
No. The host would lyse before the phage had time to replicate and assemble.
The intial decrease is due to the simple fact that many phage have injected their genomoes into hosts and are no longer infectious.
The 35S cysteine will be incorporated into viral coat proteins and the 32P phosphate will be incorporated into the viral nucleic acid genome in newly released viral particles because proteins contain no P and nucleic acids contain no S.
When these viruses infect bacteria, their nucleic acids are injected into bacteria while the capsid proteins remain on the exterior, which means only 32P will be found in the interior of the newly infected cells.
A is correct.
When two viruses infection the same cell it is called co-infection. Some normal viruses will result and some genomes from defective viruses will get packaged into capsids made from proteins encoded by the normal virus. The latter will be capable of infectiong new hosts, but when they do their progeny will not survive due to the capsid abnormality.
Why would a bacterial gene, carried by a virus integrated with viral genes into a new bacterial genome, not be repressed along with the viral genes during lysogeny?
Prophage latency results from a viral repressor protein binding to viral DNA in a sequence-specific manner. The specific DNA sequence to which the repressor binds is present in the viral genes but not in the bacterial genes, so the bacterial genes can be expressed while the viral genes are repressed.
Yes.
The soluble CD4 protein would bind to the virus’s CD4 receptor and block attachement of the virus to T cells.
- the receptor has specific role in the normal physiology of the host, which a mutation might ocmpromise.
- Viruses generally evolve so rapidlly that they can keep up with any changes in the host, but this is not an absolute rule. Cells of our immune system keep us alive by keeping up with most microorganism’s tricks.
A is correct.
Some envelope proteins are encoded by the virus and some are derived from the host’s membranes during budding.
True or False?
+ RNA viruses must encode RNA-dependent RNA polymerase and have to carry it.
False. They do have to encode RNA-dependent RNA polymerase but they don’t have to carry it.
C. Chemoheterotroph
D. Photoheterotroph
