They are not cells & having no metabolic machinery of their own, they are obligate intracellular parasites ,i.e they have to use the metabolic process of the host cell which they enter & infect.
DNA & RNA viruses
DNA Viruses:
- Poliovirus
- Rhinovirus
- Mumps, measles
- Yellow fever
- Dengue fever
- Influenza
- HIV
RNA Viruses:
- Papilloma
- Zoster
- Adenovirus
- Epstein-Barr
- Cytomegalovirus
- Herpes simplex
Types of Virus:
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DAN viruses usually enter the host cell nucleus & direct the generation of new viruses.
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RNA viruses direct the generation of new viruses ,usually without involving the host cell nucleus (the “flu “ virus is an exception in that it does involve the host cell nucleus)
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RNA retroviruses (e.g., AIDS virus ,T cell leukemia virus) contain an enzyme , reverse transcriptase , which integrates into host DNA and makes a DNA copy of the viral RNA (produces viral DNA from RNA). This copy is integrated into the host cell genome & direct the generation of new virus particles.