Characteristics of Viruses
- Microscopic
- Can onlybe seen using an electron microscope
- Non-living
- Infectious
- Do not display most of the chararistics of living things
- Do not fit into any of the 6 kingdoms
- Once inside a cell they reproduce
- Require a host
- Can be harmless, others kill their host
A host is a living cell in which viruses reproduce. They are selective when in comes tho their host cell, one type of virus enters one type of cell, like a lock and key. Viruses contain genetic instructions that take control of cells.
Structure of Viruses
Viruses vary in their individual structure, but all viruses contain two structures.
Other structures a virus could have are:
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Classificstion of Viruses
Viruses are classified differently than living things.
They are classified into:
Orders
Families
Genus
And Species
They are classified based on three pieces of information
They are classified into:
Orders
Families
Genus
And Species
They are classified based on three pieces of information
- Size
- Shape
- Type of genetic material
Virus Shapes
Virus Reproduction
There are two reproductive cycles for viruses:
There are some key differences between these two cycles. In the lysogenic cycle, the viral DNA gets injected into the host DNA. It stays within the host cell DNA and gets duplicated every time the cell replicates. Because of this it can infect you at any time. In the lytic cycle you get infected right away.
- Lytic Cycle
- Lysogenic Cycle
There are some key differences between these two cycles. In the lysogenic cycle, the viral DNA gets injected into the host DNA. It stays within the host cell DNA and gets duplicated every time the cell replicates. Because of this it can infect you at any time. In the lytic cycle you get infected right away.
Lytic Cycle
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Lysogenic Cycle
1. The virus binds to the surface of the host cell and intersects its DNA into the host cell.
2. The viral DNA forms a loop. 3A. The viral DNA instructs the host cell to make and assemble new virus parts. 4A. Lysis occurs as the host cell bursts. The newly formed go and infect more cells. 3B. In the lysogenic cycle the viral DNA gets into the host DNA . 4B. Each time the bacterium divides the viral DNA is replicated along within the bacterial DNA. 5. When the viral DNA becomes active, it separates from the host DNA and enters the lytic cycle. |
Viroids and Prions
Viroids are small infectious pieces of RNA. They are smaller than any virus and don't have a capsid. Viroids are plant pathogens that can quickly destroy entire fields of crops.
Prions cause a number of rare diseases in mammals, including mad cow disease. Prions abnormally shaped proteins found in the brain and nervous tissue of infected mammals.
Prions cause a number of rare diseases in mammals, including mad cow disease. Prions abnormally shaped proteins found in the brain and nervous tissue of infected mammals.
Vaccines
Vaccines are weakened mixtures of dangerous viruses. When injected into an individual's body a response is triggered by the immune system without causing an infection. This creates a chemical memory so the immune system can you quickly repeat it if it ever comes into contact with the real virus.
Viral Infections
Epidemic- a large scale outbreak of disease
Pandemic- a global outbreak of disease
AIDS (Human Immunodeficiency Virus)
Common Cold (rhinovirus)
Flu (influenza virus)
Herpes (herpes simplex 1 and 2 viruses)
Ebola
Smallpox
Rabies
*Encephalitis is the inflammation of the brain.
Chickenpox
Polio
Pandemic- a global outbreak of disease
AIDS (Human Immunodeficiency Virus)
- Transfer of bodily fluids
- Attacks T-cells (immune system)
- Can live symptom free for 10 years
- Symptoms: Chills, fever, rash, swollen lymph nodes
Common Cold (rhinovirus)
- Lytic in nature
- Transmitted in respiratory droplets
- Symptoms: nasal congestion, cough, fatigue, sore throat, sneezing
Flu (influenza virus)
- Direct contact with respiratory droplets
- Symptoms: nausea, fatigue, chills, headache, fever, runny nose
Herpes (herpes simplex 1 and 2 viruses)
- Typical an STI
- Transmitted by bodily fluids
- Symptoms of HS1: one or more cold sores around mouth
- Symptoms of HS2: one or more sores around genitals
Ebola
- Restricted to Africa
- Transmitted through bodily fluids
- Symptoms: confusion, malaise (haze), headache, seizures, diarrhea
Smallpox
- Transmitted though saliva
- Symptoms: fever, headache, red lesions filled with pus, fatigue
- Click here to view an image of smallpox.
Rabies
- Transmitted through saliva
- Causes encephalitis*
- Symptoms: seizures, paralysis, hallucinations
*Encephalitis is the inflammation of the brain.
Chickenpox
- Airborne disease
- Symptoms: itchy, fluid filled blisters, fever, headache
Polio
- Enters through bloodstream
- Transmitted though fecal matter
- 90% of people do not show symptoms
- Symptoms: fever, vomiting, lose of muscle reflexes, severe spasms, paralysis
- Click here to see an image of the symptoms of polio.