Chapter 19 Notes Continued

The basics of the lytic cycle:

(Youtube video: http://www.youtube.com/watch?v=wVkCyU5aeeU&feature=PlayList&p=B1AC4F7A9C99C847&playnext=1&index=33)

Attachment: The virus attaches to the host cell
Entry: The virus injects its DNA into the host cell
Replication: The virus directs the replication of its own DNA
Assembly: The new phages are assembled
Release: The host cell bursts, releasing the new viruses. These
new viruses then spread to other host cells. (Note:
the host cell is killed in the process)

The basics of the lysogenic cycle:

(YouTube video: http://www.youtube.com/watch?v=_J9-xKitsd0&feature=PlayList&p=B1AC4F7A9C99C847&index=34)

Attachment: The virus attaches to the host cell
Entry: The virus injects its DNA into the host cell
Replication: The virus' DNA combines with the host cell's DNA
and both are replicated together
Assembly: When the host cell reproduces, it also reproduces the
virus' DNA and is packaged into new host cells (The
host cell is not killed in the process)

Note: After the lysogenic cycle, the cell MAY undergo the lytic
cycle, but it doesn't have to.

Retroviruses are RNA viruses that use the enzyme reverse transcriptase to transcribe DNA from an RNA template. The new DNA then integrates into a chromosome in the nucleus of an animal cell, and the host transcribes the viral DNA into RNA. HIV is a retrovirus

Here is a website that has videos, pictures, and information on HIV/AIDS: http://www.boehringer-ingelheim.com/hiv/art/art_videos.htm

Multiple Choice:

1. What is the function of reverse transcriptase in retroviruses?
a. It uses viral RNA as a template for making complementary RNA
strands
b. It hydrolyzes the host cell's DNA
c. It uses viral RNA as a template for DNA synthesis
d. It converts host cell RNA into viral DNA
e. It translates viral RNA into proteins

2. HIV, the virus that causes AIDS, only infects certain cells within the immune system. This is because
a. the virus is not very mobile within the body and only comes into contact with a limited number of immune cells
b. other cells produce toxins that destroy the virus before infection can take place
c. the virus binds to specific receptors that are only present on certain immune cells
d. the virus gets into all cells, but the viral RNA is immediately destroyed in all but a small number of immune system cells
e.
infection requires the presence of a specific DNA sequence that is only present in the genome of certain immune system cells
3. When a virus infects an E. coli cell, what part of the virus enters the bacterial cytoplasm?
a. the entire virus
b. only nucleic acid
c. protein capsid and enclosed nucleic acid
d. tail fibers
e. only protein capsid






Answers: 1. b
2. c
3. b

from Kelli