18.1

Which of the following is (are) true about viruses?

a. Viruses are classified below the cellular level of biological organization.

Viral envelopes contain proteins with covalently attached carbohydrate groups called

a. glycoproteins.

Which of the following can be effective against viral diseases?

d. A and B only

Which of the following is a characteristic of all viruses?

d. A and B only

Viruses with single-stranded RNA that acts as a template for DNA synthesis are known as

A) retroviruses.

Which of the following statements about the lysogenic cycle of lambda ( . phage is incorrect?

C) The phage genome replicates along with the host genome.

Bacteriophage DNA that have become integrated into the host cell chromosome are called

C) prophages

Which of the following is characteristic of the lytic cycle?

D) A large number of phages is released at a time.

What is the function of reverse transcriptase in retroviruses?

D) A and C only are correct.

What is the function of the single-stranded RNA in certain animal viruses?

D) A and C only are correct.

Which of the following is not a reason scientists suspected that something other than bacteria was the cause of tobacco mosaic disease?

b. Treating infectious sap with alcohol failed to remove the infectious agent.

Which of the following is a true statement?

b. Viruses can cause diarrhea, colds, and measles.

RNA viruses appear to have higher rates of mutation because

b. replication of their genomes does not involve the proofreading steps of DNA replication.

A researcher lyses a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur?

c. The plants would develop the typical symptoms of TMV infection.

Virulent phages undergo a(n) ____ life cycle, whereas temperate phages are capable of undergoing a(n) ____ cycle.

c. lytic; lysogenic

The membrane making up the viral envelope can come from

c. the plasma membrane of an infected cell.

The simplest infectious biological systems are

c. viroids.

Viruses are referred to as obligate parasites because

d. the enzymes produced by the virus before it infects the cell.

The host range of a virus is determined by

e. both A and C

Viral genomes can consist of any of the following except

e. helical capsomeres.