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T/F Viruses are considered to be alive
T/F All viruses have the same basic structure
Viruses absolutely require a _______ cell to propagate.
In some viruses, an outer envelope is present, comprised of _____ and _____ derived from the cell membrane of their host.
All viruses are comprised of a _____ _____ surrounding the genetic material which can be either ______ or _____.
Viruses come in a wide variety of ____ and _____ and have great capacity to ______.
What problem does a viruses capacity to mutate extensively pose for the host organism?
It makes it difficult for the host organism to mount an immune response.
T/F Although viruses are not alive, they do have a life cycle that results in their reproduction.
Viral replication involves 4 steps:
1. The virus attaches to a specific type of _____.
2. The _____ material enters the host cell.
3. The viral genetic material forces the host cell to produce _____ of viral _____ and genetic material.
4. New ______ are released from the cell.
What are bacteriophages?
viruses that only infect bacteria
What type of genetic material do bacteriophages have?
The basic structure of a bacteriophage consists of a _____ and _____ region.
The head region of a bacteriophage contains the protein coat called the ______ and the ______.
The tail is made up of a tube called a ______ and some phages have several long ____ _____ connected to the base of the sheath.
The _____ region attaches to a bacterial cell and the _____ is injected into the cell through the _____.
Once the DNA is inside the cell, 2 pathways are possible. What are they?
1. Lytic cycle
2. Lysogenic cycle
What occurs during the lytic cycle?
Phage DNA instructs the cell to produce more viral particles. The cell then lyses or breaks resulting in cell death and the new bacteriophages are released and can affect other cells.
During the lysogenic cycle, once infected, the virus enters a _____ period and the host cell is neither damaged or destroyed. The phage DNA incorporates into the host cell _____ and is ______ along with the host DNA. At this stage, the virus is technically called a _____. The viral DNA is therefore passed on during cell ______. Under appropriate conditions, the phage DNA will excise itself from the chromosome and enter the _____ cycle, thus destroying the host cell.
What is a common example of an animal virus?
HIV (human immunodeficiency virus)
Some RNA viruses like HIV must have their RNA copied into DNA for the cell to use it. These viruses are called _____ and this is accomplished by the viral enzyme _____ _____.
For a retrovirus, the DNA copy is made in the _____ of the host cell and then transported into the _____ where it can incorporate with the host DNA. The virus is now called a ______ which is analogous to a ______.
Why is HIV so difficult to fight off?
It specifically targets cells in the immune system.
What do individuals with AIDS eventually die from?
Not AIDS itself, but rather from infections that can normally be fought off by a health immune system.
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