Viruses: Genes in Packages

I AM ABLE TO: Understand the process by which a virus is created.

Viruses have genes and are highly organized, but are not able to reproduce on their own and are not made of cells.

• They are basically "genes in a box".
  
• Viruses can only survive by infecting another living cell and force it to produce more viruses.


• Bacteriophages are a type of virus that attack or "eat bacteria.
• Their reproductive cycle is known as the lytic cycle.


• An alternate route is the lysogenic cycle, where the cell doesn't burst open.


• First, the virus attaches to the bacteria.



• Then it injects phage DNA into the host bacteria.


• The cell's devices for DNA transcription and translation are made to produce phages.

The phage parts are assembled, then the cell lyses, or bursts open.

• In the lysogenic cycle, after the bacterial chromosome is inserted it becomes inactive.


• The bacteria then reproduces normally, only now it has the prophage in it.


• Once in awhile, a prophage will leave the cell and send it to the lytic cycle.


• Plant viruses can stunt the plant and force the it to yield less than normal.


• Many are rod-shaped with a covering of protein spikes.


• There are no cures for plant or animal viruses.


• Hepatits, chicken pox, and herpes are examples of animal viruses.
  
• Viruses reproduce by attaching themselves to susceptible cells.


• Then, they enter the cytoplasm and remove the protein coat from the RNA that entered


• One of the enzymes that entered with the RNA, uses the RNA as a template to create mRNA.


• The mRNA are utilized to create new viral proteins and viral genome.


• They are then assembled again and exit the cell receiving an envelope.
  
• Finding ways to make anitviral drugs is hard, because it's difficult to kill the virus wothout killing the cell.


• Retroviruses like AIDS use reverse transcriptase to create RNA from the host cells own DNA.
  
• The enzyme uses the viral RNA as a template to create a new strand of DNA.


• Then it adds a second complimentary DNA strnad to form a doucle stranded virus.


• This provirus DNA attaches itself to the host cells own DNA and creates RNA.


• The RNA is then translated into viral proteins and a new virus is assembled.

Strand:Life and Environmental Sciences

Standard 5: Life and Environmental Sciences: DIVERSITY, GENETICS, AND EVOLUTION: Understand genetics and biological evolution and their impact on the unity and diversity of organisms.

Topic: Unity and Diversity

Benchmark SC.BS.5.3 Explain the structural properties of DNA and the role of DNA in heredity and protein synthesis

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