17. Viruses

Viruses can vary with respect to all of the following characteristics except __________.

A microbiologist analyzes chemicals obtained from an enveloped RNA virus that infects monkeys. He finds that the viral envelope contains a protein characteristic of monkey cells. Which of the following is the most likely explanation?

Which of the following, if any, may be a component of a virus?

Viruses that infect bacteria are called __________.

HIV, the virus that causes AIDS, only infects certain cells within the immune system. This is because __________.

Which of the following can a virus do without a host cell?

When a virus infects an E. coli cell, what part of the virus enters the bacterial cytoplasm?

The phage reproductive cycle that kills the bacterial host cell is a __________ cycle, and a phage that always reproduces this way is a __________ phage.

In the lytic life cycle of phages, __________.

Restriction enzymes help defend bacteria against viral infections by __________.

The avian flu virus H5N1 is considered a greater long-term threat than the swine flu virus H1N1 because __________.

A new pathogenic form of influenza A can emerge when __________.

Plant viruses spread throughout the plant by way of __________.

Which of the following is an example of vertical transmission of a virus in plants?

Birds act as a natural __________ for the influenza __________ virus.

A phage that inserts itself into the host DNA is called __________.

A prophage is a(n) __________.

In the lysogenic cycle of phages, __________.

What is the origin of the phospholipid membrane that envelops many animal viruses?

What is the function of hemagglutinin in the influenza virus?

Why can flare-ups of herpesvirus infection recur throughout a person's life?

How do retroviruses, such as HIV, differ from other viruses?

Emerging viruses can originate from which of the following sources?

Reverse transcription, carried out by retroviruses, is the process by which __________.

Which statement below is a correct comparison of a "regular" RNA virus and an RNA retrovirus?

When comparing DNA and RNA viruses, which mutate more quickly, and why?

The symptoms of a viral infection in a person can be caused by __________.

Vaccines for viral diseases are __________ and help prevent infection by __________.

Prions are __________ that are thought to cause disease by __________.

What features distinguish the seven major categories of viruses?

Compare and contrast the bacteriophage lytic cycle and lysogeny by addressing (1) the rate of replication of the viral genome, (2) production of virions, and (3) effect on the host cell.

If you come down with the flu, should your physician prescribe an antibiotic for you? Explain why or why not.

Of the viruses highlighted in Section 33.4, predict which of the following would be able to make viral proteins if nothing more than its genome were injected into a suitable host cell. a. pea mosaic ([+]ssRNA) virus b. bluetongue (dsRNA) virus c. measles ([−]ssRNA) virus d. human immunodeficiency (RNA reverse-transcribing) virus

Which of the following is/are always true? a. Viruses cannot reproduce outside a host cell; b. Viruses are not surrounded by a membrane; c. Viruses are not made up of cells; d. A and C are correct; e. A, B, and C are correct

The mosquito-borne Zika virus (ZIKV) is one of the most feared viruses for pregnant women. Recent statistics justify this fear: Infants born to mothers infected with ZIKV during pregnancy face a risk of up to 42 percent of developing birth defects, including microcephaly (an abnormally small head and decreased brain volume). What do we know about how ZIKV causes damage to the developing brain? Several lines of evidence suggest that after ZIKV is transmitted to a pregnant woman via the bite of an infected mosquito, the virus then directly infects cells of the placenta, gaining access to the fetal brain. Following attachment, the virion would most likely enter the placental cell by: a. insertion via the mosquito's mouthparts b. endocytosis c. degrading the cell wall with lysozyme d. injection through a hollow, needle-like protein structure

The mosquito-borne Zika virus (ZIKV) is one of the most feared viruses for pregnant women. Recent statistics justify this fear: Infants born to mothers infected with ZIKV during pregnancy face a risk of up to 42 percent of developing birth defects, including microcephaly (an abnormally small head and decreased brain volume). What do we know about how ZIKV causes damage to the developing brain? Traveling and tourism have been badly affected in ZIKV-affected countries. What advice would you give a friend planning a trip to the Caribbean?