Viral Structure and Life Cycles : Notes

Name : ______Date : ______

VIRUSES : Viral Structure and Life Cycles : Notes #1

A) Structure of a Virus

-Composed of a core of ______

surrounded by a ______

______

-The Capsid ______the nucleic acid core.

-Nucleic Acid can be ______but never both. (retroviruses contain RNA)

-The ______helps attach the virus to the cell

-The ______the nucleic acid into the cell.

- The picture shown above is that of a ______

______

- There are three main shapes of Viruses. See pictures below:

______

B) Biotic( ______) or ______(______) **Viruses straddle the fence between living and non-living ALIVE Non-Living - Have DNA or RNA and ______- Acellular – not made of cells (No non-living thing contains ______/protein) - ______- Can ______- ______- Have ______- Do not move - Can reproduce** *** Do ______- Demonstrate some level of being able ______to ______

** Some biologists describe viruses as being non-living infectious particles

C) Viral Life Cycles - Two main types of Life Cycles (Viral Replication) for viruses: 1) -______2) -______

1) LYTIC CYCLE OF A VIRUS: - In the Lytic Life Cycle (shown below),______

______

______.

______This process takes place very quickly.

- Viruses that reproduce through a lytic cycle are ______

- ______: A virus that makes many copies of itself in its host cell; ______and release the reproduced viruses to spread to many more host cells.

- This process only takes about ______from beginning to end.

2) LYSOGENIC CYCLE OF A VIRUS

- Another way in which some viruses affect a cell is through a ______

______. The virus does not reproduce and lyse of the host cell (as was the case in the lytic cycle) – at least not right away.

-______

______

- Like the Lytic Cycle, the DNA of the virus is injected into the host cell.

- Once integrated into the Host cell’s DNA, the viral DNA is known as

______

- The PROPHAGE may remain combined as part of the DNA of the host cell for many generations. ______. - As long as this prophage (viral DNA) does not cause lysis it is considered to be - acting as a ______, sometimes a temperate phage will get triggered (______) to enter into the

Lytic Cycle. This temperate phage now becomes a ______

______