virus replication

• attachment - the virus attaches to the host cell
• entry - the virus forms a hole in the host cell and the nucleic acid of the virus is pushed through - the protein coat of bacteriophages stay outside the bacterium cell but when viruses enter animal cells the protein coat enters as well but is digested
• synthesis - the host DNA becomes inactive - the viral nucleic acid used the hosts' organelles to produce new viral nucleic acids and proteins
• assembly - new viruses are made inside the host cell
• release - the host cell bursts to release the new viruses - this bursting of the host cell is called lysis
• a retrovirus contains RNA instead of DNA and an enzyme that changes the viral RNA into DNA - the virus that causes AIDs is a retrovirus
• human diseases cause medical problems resulting in economic losses and time lost at work
• viruses cause plant dieases like the tobacco mocaic
• viruses cause animal diseases like rabies in dogs
• viruses cause human diseases like the flu, colds and chicken pox
• they can sometimes be used to transfer genes from one organism to another in genetic engineering
• bacteriophages may be used to control some baterical infections
• they provide restriction enzymes that are used to cut DNA strands in genetic engineering
• viruses are controlled by the body's general defence system (skin, stomach acid) and by the specific defence system (antibodies produced by white blood cells)
• vaccinations can be used for protection against some viral diseases (MMR vaccination)
• antibodies have no effect on viruses
• drugs like interferon and acyclovir have been developed to interfere with viral replication