BIO 21

bacteria

A bacteriophage can infect ________. a. the lungs b. viruses c. prions d. bacteria

The host cell can continue to make new virus particles.

Figure Influenza virus is packaged in a viral envelope that fuses with the plasma membrane. This way, the virus can exit the host cell without killing it. What advantage does the virus gain by keeping the host cell alive?

Glycoproteins help the virus attach to the host cell.

Figure Which of the following statements about virus structure is true? a. All viruses are encased in a viral membrane. b. The capsomere is made up of small protein subunits called capsids. c. DNA is the genetic material in all viruses. d. Glycoproteins help the virus attach to the host cell.

An environmental stressor can cause the phage to initiate the lysogenic cycle.

Figure Which of the following statements is false? a. In the lytic cycle, new phage are produced and released into the environment. b. In the lysogenic cycle, phage DNA is incorporated into the host genome. c. An environmental stressor can cause the phage to initiate the lysogenic cycle. d. Cell lysis only occurs in the lytic cycle.

Plant viruses infect crops, causing crop damage and failure, and considerable economic losses.

Although plant viruses cannot infect humans, what are some of the ways in which they affect humans?

They both replicate in a cell, and they both contain nucleic acid.

How are viroids like viruses?

Plant viruses infect crops, causing crop damage and failure, and considerable economic losses.

In this section, you were introduced to different types of viruses and viral diseases. Briefly discuss the most interesting or surprising thing you learned about viruses.

either RNA or DNA

Oncogenic virus cores can be_______. a. RNA b. DNA c. neither RNA nor DNA d. either RNA or DNA

This prion-based disease is transmitted through human consumption of infected meat.

Prions are responsible for variant Creutzfeldt-Jakob Disease, which has resulted in over 100 human deaths in Great Britain during the last 10 years. How do humans obtain this disease?

Viruses pass through filters that eliminated all bacteria that were visible in the light microscopes at the time.

The first electron micrograph of a virus (tobacco mosaic virus) was produced in 1939. Before that time, how did scientists know that viruses existed if they could not see them? (Hint: Early scientists called viruses "filterable agents.")

both b and c

The viral ________ plays a role in attaching a virion to the host cell. a. core b. capsid c. envelope d. both b and c

stimulate an immune response

Vaccines_______. a. are similar to viroids b. are only needed once c. kill viruses d. stimulate an immune response

Newly released virions can infect adjacent cells.

Which statement is not true of viral replication? a. A lysogenic cycle kills the host cell. b. There are six basic steps in the viral replication cycle. c. Viral replication does not affect host cell function. d. Newly released virions can infect adjacent cells.

It transcribes RNA to make DNA.

Which statement is true of reverse transcriptase? a. It is a nucleic acid. b. It infects cells. c. It transcribes RNA to make DNA. d. It is a lipid.

Viruses are acellular.

Which statement is true? a. A virion contains DNA and RNA. b. Viruses are acellular. c. Viruses replicate outside of the cell. d. Most viruses are easily visualized with a light microscope.

no cell within the dog that is permissive for viral replication.

Why can't dogs catch the measles?

Reverse transcriptase is needed to make more HIV-1 viruses, so targeting the reverse transcriptase enzyme may be a way to inhibit the replication of the virus.

One of the first and most important targets for drugs to fight infection with HIV (a retrovirus) is the reverse transcriptase enzyme. Why?

vary in shape

Viruses_______. a. all have a round shape b. cannot have a long shape c. do not maintain any shape d. vary in shape

They use the host cell's machinery to produce new copies of their genome.

Which is true of DNA viruses? a. They use the host cell's machinery to produce new copies of their genome. b. They all have envelopes. c. They are the only kind of viruses that can cause cancer. d. They are not important plant pathogens.

antibiotics

Which of the following is NOT used to treat active viral disease? a. vaccines b. antiviral drugs c. antibiotics d. phage therapy

DNA

Which of the following is not associated with prions? a. replicating shapes b. mad cow disease c. DNA d. toxic proteins

During attachment, the virus attaches at specific sites on the cell surface.

Which statement is true of viral replication? a. In the process of apoptosis, the cell survives. b. During attachment, the virus attaches at specific sites on the cell surface. c. The viral capsid helps the host cell produce more copies of the viral genome. d. mRNA works outside of the host cell to produce enzymes and proteins.

They are single-stranded RNA particles.

Which statement is true of viroids? a. They are single-stranded RNA particles. b. They reproduce only outside of the cell. c. They produce proteins. d. They affect both plants and animals.

Rabies vaccine works after a bite because it takes week for the virus to travel from the site of the bite to the central nervous system, where the most severe symptoms of the disease occur. Adults are not routinely vaccinated for rabies for two reasons: first, because the routine vaccination of domestic animals makes it unlikely that humans will contract rabies from an animal bite; second, if one is bitten by a wild animal or a domestic animal that one cannot confirm has been immunized, there is still time to give the vaccine and avoid the often fatal consequences of the disease.

Why is immunization after being bitten by a rabid animal so effective and why aren't people vaccinated for rabies like dogs and cats are?