What is a virus?

•Microscopic particles (microbe) that invade the cells of living organisms.

Viral Characteristics…

Viruses are not living organisms!

Living Characteristics

Contain genetic information –DNA or RNAHeredity- do pass genetic information to next generationCan reproduce

Non-Living CharacteristicsNot cells- can’t make proteins.Can’t make or use energy.Can’t survive or reproduce without a host.

What does a virus look like?

• Viruses have many different shapes and sizes, but all viruses are smaller than bacteria cells.

Basic Structure of Virus

• Core-

nucleic acid (DNA or RNA)• Capsid-

protein coat surrounds core

In order to exist and reproduce,

a virus must invade

a living cell.

This living cell is referred to as a host.

Viral Reproduction

Steps of viral reproduction:

• Recognition

• Attachment

• Injection

• Assembly

• Lysis

Lytic Viruses

• This type of virus replicates immediately and kills the host cell.

• Virus enters host, replicates, causes host to burst= lysis.

Lysogenic Virus

Virus does NOT kill host immediately.Viral nucleic acid “fuses” with the host cell nucleic acid.Lysogenic viruses have a “dormant” period.Results in many cells being “infected.”HIV is a lysogenic virus

Lysogenic Virus

PROPHAGE

(VIRAL DNA)