Viruses

• Viruses are responsible for many diseases and illnesses.

• Some are deadly and others can cause permanent damage, while others still only cause temporary damage and your body can recover.

• Some diseases caused by viruses: Polio, Influenza, AIDS, Warts, Rabies, Colds, Hepatitis

• There are two main categories of viruses, DNA or RNA.

• Characteristics of a virus:

•Sub-cellular, (very small) 25nm to 250nm

•They have no nucleus, organelles, cytoplasm, ribosome’s, or membrane.

• Show only one characteristic of life: Reproduction

• Viruses do not have: locomotion, metabolism, any other life function.

• Can only reproduce when in a living cell.

• Parts of a Virus

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A VIRUS is a microscopic particle, made of either DNA or RNA, that is protected by a protein coat called a CAPSID.

DNA

CAPSID

VIRUSCapsid - is an outer protein coat which is wrapped around a central core of a highly complex chemical called nucleic acid. The capsid helps the virus to attach to its host cell

Nucleic Acid - either RNA or DNA, contains the information necessary for viral reproduction.

Why are some viruses harmful?

Virus invades cell

Virus forces cell to make copies of virus

Eventually so many copies are made, the cell explodes,releasing all of the new viruses

When your cells make viruses instead of operating normally, YOU get sick

DISEASE VIRUSES

AIDS HIV

WartHerpes Simplex Virus

Flu Influenza

Measles Morbillivirus .

Cancer Hepatitis B

Examples of some viral diseases:

Viral StructureViruses can be one of 3 shapes:

• Rod shaped

• Spherical

•Bacteriophage(virus that attacks bacteria)

Ex 1 - Tobacco Mosaic Virus

Ex 2 - Herpes

Simplex Virus Ex. 3 – Bacteriophage

• 1. Attachment to host cell

• 2. Entry of nucleic acid into the host cell

• 3. Viral DNA replication

• 4. Synthesis of virus particles

• 5. Assembly of virus particles

• 6. Release of virus progeny (this may or may not destroy the host cell)

How viruses infect: the Lytic Cycle.

The Retrovirus - HIV and AIDSWhy is HIV different?

• The HIV virus attacks T-cells in the immune system, eventually causing AIDS (acquired immunodeficiency syndrome).

• HIV progressively destroys the body's ability to fight infections and certain cancers.

• People diagnosed with AIDS may get life-threatening diseases called opportunistic infections, which are caused by microbes such as viruses or bacteria that usually do not make healthy people sick.

• In other words: HIV is different, because it directly attacks the body’s ability to regain healt

• HIV is an RNA virus.

• It contains an enzyme that causes the host cell to copy RNA into DNA which is incorporated into the chromosomes of a cell.

• the provirus can continue to produce viruses at a low level, without harming the host cell.

• HIV infected people can remain healthy for many years because of this.