3 Main Questions:
- What is capsid?
The protein shell enclosing the viral genome.
- What is phages?
A virus that infects bacteria; also called a bacteriophage.
- What is viral envelope?
A membrane that cloaks the casid that in turn encloses a viral genome.
5 Main Facts:
- Some viruses have accessory structures that heko them infect their hosts.
- A viral infection begins when a virus binds to a host cell and the viral genome makes its way inside.
-Phages are the best understood of all viruses, although some of them are also among the most complex.
- There are many variations on the simplified viral reproduction cycle we have traced in this general description.
- Most DNA viruses use the DNA polymerases of the host cell to synthesize new genomes along the templates provided by the viral DNA.
Diagram:
Viruses are made up of nucleic acid (DNA or RNA) enclosed in a protein coat (the capsid) and sometimes further wrapped in a membranous envelope. The individual protein subunits making up the capsid are called capsomeres. Although diverse in size and shape, viruses have common structural features, most of which appear in the diagram.
Summary:
To large extent, molecular biology was born in the laboratories of biologists studying viruses that infect bacteria. Beyond their value as experimental systems, viruses have unique genetic mechanisms that are interesting in their own right.
Experiments with viruses provided imoportant evidence that genes are made of nucleic acids, and they were critical in working out the molecular mechanisms of the fundamental processes of DNA replication, transcription, and translation.
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