AP BIO: Chapter 18

What are prions?

A) misfolded versions of normal brain protein

DNA is transferred from one bacterium to another by a virus

A. transduction

What does bacterial mating involve?

B) formation of a conjugation tube for the transfer of male DNA

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

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

An R plasmid can

a. facilitate bacterial resistance to antibiotics.

Viral envelopes contain proteins with covalently attached carbohydrate groups called

a. glycoproteins.

In biotechnology, genes are commonly introduced into bacterial cells by incubating the cells together with DNA and high concentrations of calcium ions. This is an example of

e. transposition.

Which of the following contributes to the emergence of viral disease?

d. A and B only

Which of the following is a characteristic of all viruses?

d. A and B only

What is the most common source of genetic diversity in a bacterial colony?

e. mutation

Which treatment could definitively determine whether or not the component is a viroid?

A) I

An Hfr bacterium is one that has

A) a plasmid that has become integrated into its chromosome.

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

A) retroviruses.

What does the operon model attempt to explain?

A) the control mechanism of gene expression in bacteria

The role of a metabolite that controls a repressible operon is to

B) bind to the repressor protein and activate it.

The difference between vertical and horizontal transmission of plant viruses is that

A) vertical transmission is transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant.

A sequence of DNA is moved to alternative locations within the genome

B. transposition

If you already knew that the infectious agent was either bacterial or viral, which treatment would allow you to distinguish between these two possibilities?

C) III

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

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

A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in

C) continuous transcription of the structural gene controlled by that regulator.

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

C) prophages

All of the following are made up of nucleic acid except a

C) repressor.

Transcription of the structural genes in an inducible operon

C) starts when the pathway's substrate is present.

Of the following, which is least related to the others?

C) transposon

A mutation in this section of DNA could influence the binding of RNA polymerase to the DNA.

C. promoter

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 characteristic of the lytic cycle?

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

Which treatment would you use to determine if the agent is a prion?

D) IV only

For a repressible operon to be transcribed, which of the following must be true?

D) RNA polymerase must bind to the promoter and the repressor must be inactive.

Which of the following statements regarding transposons is not true?

D) Transposons are genes that encode sex pili and enable plasmid transfers between bacteria.

The tryptophan operon is a repressible operon that is

D) turned off whenever tryptophan is added to the growth medium.

This protein is produced by a regulatory gene.

D. repressor

External DNA is assimilated by a cell.

D. transformation

A group of F+ bacteria is mixed with a group of F- bacteria. After several days, all of the bacteria are F+.

E. conjugation

A plasmid is exchanged between bacteria through a pilus

E. conjugation

A lack of this nonprotein molecule would result in the inability of the cell to "turn off" genes.

E. corepressor

Most molecular biologists think that viruses originated from fragments of cellular nucleic acid. Which of the following observations supports this theory?

E) Viral genomes are usually more similar to the genome of the host cell than to the genomes of viruses that infect other cell types.

How does active CAP induce expression of the genes of the lactose operon?

E) control the binding of RNA polymerase to the operator region

The lactose operon is likely to be transcribed when

E) both C and D 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 statements about operons is (are) true?

b. Tryptophan itself can bind to the trp operator and shut down production of tryptophan pathway enzymes.

Which of the following is a true statement?

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

Which of the following represents a difference between viruses and viroids?

b. Viruses have capsids composed of protein, whereas viroids have no capsids.

RNA viruses appear to have higher rates of mutation because

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

Allolactose induces the synthesis of the enzyme lactase. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following occurs when the lactose enters the cell?

c. Allolactose binds to the regulator.

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.

A scientist is studying a strain of bacteria that commonly transfers genes to other bacteria. Which of the following would provide evidence that the genes are being transferred through specialized transduction?

c. The same one or several gene(s) are always transferred.

Which of the following is true of plant virus infections?

c. They have little effect on plant growth.

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.

Which of the following can be effective against viral diseases?

d. A and B only

The process by which host cell DNA is accidentally packaged within a phage capsid and transferred to another cell instead of the phage DNA is called

d. generalized transduction.

Reproduction in bacteria requires

d. replication of DNA.

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.