Matt- Biology- 19-2
What is the structure of a typical virus?
A typical virus in composed of a core of either DNA or RNA surrounded by a protein coat.
Why viruses not considered alive?
If consider living things be made up of cells and be able to live independently--------viruses must infect a living cell in order to grow and reproduce (parasite)
What is prophage?
It is the viral DNA that is embedded in the host's DNA
What occurs when viruses get inside of cells?
Once inside, the viral genes are expressed. The cell transcribes and translates the viral genetic information into viral capsid proteins. Sometimes the program may cause the cell to make copies of the virus, and in the process the host cell is destroyed.
What happens in a lytic infection?
The bacteriophage attaches to the bacterium's cell wall. The bacteriophage injects its DNA into the cell. The cell makes mRNA from the bacteriophage's genes. The virus wrecks the cell, causing it to burst. The bursting of the cell releases new bacteriophage particles
Why is a lytic infection given that name?
The host cell is lysed and destroyed.
What are viruses?
They are particles of nucleic acid, protein, and in some cases lipids that can reproduce only by infecting living cells.
What are retroviruses?
They are viruses that contain RNA as their genetic information.
What are bacteriophages?
They are viruses that infect bacteria
What do all viruses have in common?
They enter living cells and, once inside, use the machinery of the infected cell to produce more viruses.
What happens when retroviruses infect a cell?
They produce a DNA copy of their RNA. This DNA is inserted into the DNA of the host cell.
Why are most viruses hightly specific to the cells they infect?
Viruses must bind precisely to proteins on the cell surface and then use a host's genetic system.
What happens in a lysogenic infection?
a virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell's DNA. These viruses do not lyse the host cell right away. Instead it remains inactive for a period of tiem
Living Characteristics of viruses--
after infecting living cells, viruses can reproduce, regulate gene expression, and even evolve.
A virus' protein coat is called
capsid--includews proteins that enable a virus to enter a host cell.
How does a typical virus get inside a cell?
the capsid proteins bind to receptors on the surface of a cell and "trick" the cell into allowing it inside.
Most viruses are so small,
they can be seen only with the aid of a powerful electron microscope
