In the lysogenic cycle, the virus reproduces by first injecting its genetic material, indicated by the red line, into the host cell's genetic instructions.
Viruses enter bacterial cells by punching a hole in the cells wall and injecting its DNA
Viruses Enter Living Cells
Viruses enter plant cells through tiny rips in the cell wall.
Viruses enter animal cells by endocytosis.
Viruses can mutate when they copy the genetic material
Copy something wrong
Mistake proves useful
More powerful virus (more infectious)
Viruses don’t mutate often, except…
Viruses are host cell specific.
Most viruses are restricted to certain kinds of cells (those that infect plants cannot infect animal cells).
Scientists think that viruses originated from escaped genetic material from host cells.
Viruses can be beneficial…
Bacteriophages – attack & destroy bacteria
Baculovirus – ebola-like virus that attacks insects
Could use for pest control in crops
Cabbage loopers eat
Virus can kill pests in days
(it’s really gross)
… and then there are those that are not so good….
The spread of West Nile virus (1999 – 2002) – bird, horse, mosquito or human
Any agent (not just viruses) that causes disease is a pathogen.
When a virus inserts its genetic material into a host’s DNA, it is called a provirus.
Some viruses replicate very slowly and only cause damage when the conditions are “right”. (cold sores)
Viral envelope – lipid bilayer; glycoproteins protrude from surface
Glycoproteins enable virus to recognize surface proteins of special immune cells and to enter the cell (like a key to the cell’s door)
2 strands RNA – only 9 genes; 3 are found in many viruses (structural proteins)