Date post: | 10-May-2015 |
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VIRUSES
VIRUSESAvian
influenza AH5N1 virus
VIRUSES
Virus Definition & Criteria• infectious agent with both
living and nonliving characteristics that is totally dependent on a host cell for replication (intracellular parasite)
• contain only either DNA or RNA, but not both
• viral genome directs the synthesis of viral components using host cell machinery
VIRUSES
Virus Definition & Criteria• newly synthesized viral
components are assembled into a new complete virus called a virion (pronounced vye-ree-on) which can then infect another host cell
• bacteriophage: virus that infects only bacteria
• mycophage: virus that infects only fungi
VIRUSES
Multiple virions of
yellow fever virus, the
first human virus
discovered in 1901.
Living characteristics of viruses • reproduce at a fast rate, but only in
living host cells• can mutate / evolve
Nonliving characteristics of viruses
• are acellular (no cytoplasm or organelles)
• not autonomous: carry out no metabolism on their own (i.e. viruses don't grow and divide)
• replication is fully dependent on the host cell's metabolic machinery; viral components are synthesized and assembled within the infected host cell
VIRUSES
VIRUSES
SARS related Corona viruses
Viral SizeViruses are usually much smaller than bacteria and are submicroscopic. Most range in size from 5 to 300 nm. Thus viruses can infect even other microorganisms.
Animal RNA Virus
Animal DNA Virus Bacteriophage
Viral Structure
A virus consists of these main parts:
• Genome (DNA/RNA)• Capsid (protein)• Envelope (lipid) capsid
genome
VIRUSES
Genome
• Genetic material of the virus that codes for the synthesis of viral components and viral enzymes for replication
• Can be DNA or RNA but not both
• Can be single or double stranded
• Can be a circular or linear molecule
• Can be a single unit or segmented into parts
VIRUSES
Which Human Diseases Are Caused By Viruses?
• Infectious diseases
DNA viruses
Respiratory disease
Smallpox
Chicken pox
Mononucleosis
Cold sores
RNA viruses
AIDS
Influenza (flu)
Common cold
Polio
Measles
Rabies
VIRUSES
Capsid (core)
• A protein shell surrounding the genome.
• Protects and introduces the genome into host cells.
• Viruses that consist of only a genome surrounded by a capsid and are called nucleocapsid or naked viruses.
Nucleic acid
Envelope
Capsid
VIRAL STRUCTURE
Envelope
• Most animal viruses have an envelope
• Composed of phospholipids and glycoprotein
• Usually derived from host cell membranes by a process called budding.
Nucleic acid
Envelope
Capsid
VIRAL STRUCTURE
Electron Micrograph of HIV Budding from a T4-Lymphocyte
Virus Obtaining Its Envelope from Host Cell Membrane by Budding
VIRAL STRUCTURE
Chicken Poxvaricella-zoster virus (VZV)
DNA Virus
PolioPoliovirus
RNA Virus
It is found in areas where water treatment and sanitation facilities are not properly maintained or non-existent. Although children under three years of age represent more than half of all cases polio can affect people of any age.
Nonparalytic polio causes symptoms that mimic the flu. Sore throat, fatigue, nausea, diarrhea, a fever, or vomiting. Most cases of nonparalytic polio clear up in a number of days, but a some people go on to develop meningitis, a condition in which the lining of the brain is infected. When a person develops paralytic polio, destroys nerves that control muscles. The infection may be fatal if the brain and respiratory organs become affected.
Polio is a serious condition that causes paralysis in about 1% of those infected (paralytic polio).
HerpesDNA Virus
Herpes Simplex 1 and herpes simplex 2.
The sores are sometimes accompanied by other symptoms such as:headache, fever, and other flu-like symptoms pain, itching, tingling, or tenderness around the genitals painful urination, swollen tender points in the groin and lower abdomen
HIV – Human Immunodeficiency Virus
HIV MYTHS
http://www.youtube.com/watch?v=LaVm3moZo_g
http://www.youtube.com/watch?v=68I7JlVhuhY&feature=related