02-04b Viruses

Koch’s postulates state that -

• viruses are living things.

• viruses are nonliving things.

• a given pathogen can cause a given disease.

• viruses are the only pathogens that cause disease.

Why are viruses considered nonliving things?

• Viruses do not adapt to their environment.

• Viruses do not have DNA.

• Viruses harm all living things.

• Viruses cannot reproduce without a host.

What do vaccines encourage the body to produce in order to build up immunity?

• Oxidizing agents

• Memory cells

• Antibodies

• Antigens

Which of the following 2 statements are the reasons that scientists say a virus is non-living?

• They cannot reproduce without a host and they are not made of cells.

• All options are correct.

• They are small and need a host.

• They are made of cells and they reproduce on their own.

A bacteriophage lytic infection concludes (ends) with the -

• embedding (putting) of viral DNA into the host cell’s DNA.

• production of a prophage.

• bursting (exploding) of the host cell.

• production of messenger RNA.

How does an influenza virus get into an animal cell?

• The virus is absorbed by endocytosis.

• The virus injects itself into the cell.

• The viral DNA has always been there, but has been dormant.

• The virus does not get into the cell.

What do traditional vaccines introduce into the body?

• Lethal viruses

• Dead or modified viruses

• Helper T cells

• Bacteriophages

Unlike bacteriophage lytic viruses, lysogenic viruses do NOT -

• inject (put) their genetic material into the host cell.

• enter the lytic cycle.

• lyse (burst) the host cell right away.

• infect host cells.

Viruses cause infection by -

• producing toxins that harm the body.

• reproducing independently inside the body.

• forming endospores in the body.

• entering body cells and replicating.

How do viruses reproduce?

• They divide by mitosis.

• Sexually, by external fertilization.

• Inserting DNA into the host cell.

• Replication outside the host cell.