A virus is a _________________ life form that reproduces only inside a _________________. They exhibit some but not all of the characteristics of living things. Viruses contain ______________ & ___________ ________________. A ___________ is the living cell in which the virus reproduces. In 1933, Wendell Stanley discovered that viruses are _____________ & not living things with his experiment with Tobacco Mosaic Virus.
Viruses range in size from ____________ to ___________. They consist of 2 parts:
1) __________________________, & 2) ____________________________. The inner core contains _______ or _________ (never both). The __________ is an outer ________________ that makes up 95% of the body of the virus. The ______________ is a membrane that surrounds the capsid & helps it to gain entry into cells (it contains proteins, lipids, & glycoproteins derived from the host cell). A _____________________ is a virus that invades bacteria. It attacks by adhering to a cell wall & injecting its _______________________ that alter the bacterium’s genetic code. (Review Hershey & Chase’s work with bacteriophages). Animal viruses enter their host through ____________________.
The reproductive cycle of a virus consists of 2 cycles: the _____________________ & the ______________________________.
The ________________________ consists of the virus killing the _____________. It has 5 stages.
1. ______________________ - the phage attaches itself to the cell wall – a chemical bond forms between sites on the tail of the virus & sites on the cell wall – this is like a lock & key
2. ______________________ - The phage releases _______________ that break down the wall – the tail is forced through the weakened wall – the ____________________ of the phage passes through the hollow tail into the host – the empty _____________ is left outside
3. ______________________ - the virus copies itself in the cell - _______ or ________ enters the host’s chromosomes & makes a template from its own – the organism now makes viral proteins & viral RNA
4. ______________________ - viral nucleic acids & proteins are assembled into new particles called _________________________
5. ______________________ - new phages release an enzyme that weakens the cell wall – the host cell _____________ & releases newly created ___________ - up to 300 new viruses can be produced in 1 cell
The ____________________________ is considered to be an inactive cycle & may stay this way for several generations. It has 3 stages.
1. _____________________ - the _____________________ of the invading phage attach to the DNA of the host cell – this is now called a __________________
2. ______________________ - the prophage is now replicated along with the DNA of the host
3. ______________________ - the prophage enters the __________ cycle & makes new viral parts
______________________________ is the ability to transfer genetic information from 1 host to another. This process alters the hereditary code of a cell. There are 2 types:
1) _____________________ - random fragments transfer from the host to the receiver
2) _____________________ - special genes transfer from 1 cell to another
_________________________ are disease-causing organisms. _____________________ refers to the ability to cause disease. A virus’ virulence depends on 1) ____________________________, 2) _______
________________________, & 3) ______________________________. The body’s natural defense against disease is referred to as __________________________. Cells called _________________ engulf & destroy invading organisms. An ___________________ is a foreign protein or virus while ___________ are produced by the body to fight them. ______________________________ is achieved when the body has actually been exposed to antigens through the pathogen itself or through a _________________. This process stimulates the production of antibodies. ________________________ is received from the antibodies produced in another person or animal that has developed immunity. This is only temporary.
________________________________ is a protein that interferes with viral replication. This protein attacks any type of virus but is species specific.
A ___________________ is deadly because it transcribes DNA from an __________________________& inserts this into the host. This is made possible by ________________ ______________________. These viruses can have a lengthy latent period. Examples are ____________ & _________________.
_____________ are “protein infectious particles” that contain no DNA or RNA. These typically infect the brain (mad cow disease).
COMMON VIRAL DISEASES
Chickenpox –
Measles –
Rubella –
Mumps –
Smallpox –
Hepatitis –
Polio-
AIDS –
Influenza –
Common Cold -