11.2 Viruses

Characteristics of Viruses

are _______ since they have __ ___________ and are not classified in any kingdom of living things

have no organelles, _______ or __________ and rely upon other living organisms to reproduce

Characteristics of Viruses

consist of DNA or RNA strands contained within a protective protein coat called a _______

the capsid protects the virus from attack by host cells and is a means by which viruses are classified

Characteristics of Viruses

shapes of capsids: polyhedral, spherical, cylindrical, polyhedral with a protein tail

Exs.

Characteristics of Viruses

Viruses are also classified by the type of ________ they contain, DNA or RNA and by the types of _______ they cause

DNA and RNA Viruses1) DNA viruses: ____ _____ and follow the lytic cycle able to be detected and destroyed by the human

immune system2) RNA viruses: most virulent and can remain

__________ for a period of days or months or even years

Follow the ____________ but once they are active in a host they can be detected by the immune system

Cause diseases like _______, rabies and ________

Viral Reproduction

There are 2 types of viral reproduction :

1) Lytic Cycle

2) Lysogenic Cycle

Lytic Cycle

1) virus attaches to the _______ of the host cell2) virus injects its nucleic acid into the

bacterial cell and takes over the host mRNA3) the host cell replicates the viral DNA4) new virus particles are then _______ in the

cell and then released through cell ______5) the new particles attack neighbouring cells

Lysogenic Cycle

1) the __________ becomes attached to cell wall

2) viral DNA is _______ into the host cell

3) viral DNA inserts itself into the host cell DNA by _________

4) when the host cell reproduces its genetic content, the ________ are also replicated

Lysogenic Cycle (cont’d)

5) for many generations, there are no active viral particles produced

6) occasionally, the viral DNA will become active in a host cell (_______ which triggers reproduction)

7) bacterium lyses, releasing new viruses

8) phages carry genes from host cell to neighbouring cells

Retroviruses When an RNA virus enters a host

cell it must first convert its ___ to ____

This is done using a special enzyme called ______________, which the RNA virus carries

It is now able to _____ the viral ___ into the host genome and follows the _________ cycle