ap bio chapter 19

What are prions?

A) misfolded versions of normal brain protein

A linear piece of viral DNA of 8 kb can be cut with either of two restriction enzymes (X and Y). These are subjected to electrophoresis and produce the following bands: (refer to figure) Cutting the same 8 kb piece with both enzymes together results in bands at 4.0, 2.5, 1.0, and 0.5. Of the possible arrangements of the sites given below, which one is most likely?

B

SQ - A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced would have

D) T4 protein and T4 DNA.

What characteristics of electron microscopes make them most useful for studying viruses?

D) shorter wavelengths providing higher resolution

In 1971, David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA. The table below shows the results of testing five viruses for nuclease specificity, the ability of the virus to act as an mRNA, and presence (+) or absence (-) of its own viral polymerase. (refer to table) Based on the above table, which virus meets the requirements for a bacteriophage?

A

You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope III. culturing the substance by itself on nutritive medium, away from any plant cells IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious Which treatment could definitively determine whether or not the component is a viroid?

A) I

Why are viruses referred to as obligate parasites?

A) They cannot reproduce outside of a host cell.

Which of the following is the best predictor of how much damage a virus causes?

A) ability of the infected cell to undergo normal cell division

Which of the following can be effective in preventing viral infection in humans?

A) getting vaccinated

Which of the following molecules make up the viral envelope?

A) glycoproteins

Most human-infecting viruses are maintained in the human population only. However, a zoonosis is a disease that is transmitted from other vertebrates to humans, at least sporadically, without requiring viral mutation. Which of the following is the best example of a zoonosis?

A) rabies

What is the name given to viruses that are single-stranded RNA that acts as a template for DNA synthesis?

A) retroviruses

The host range of a virus is determined by

A) the proteins on its surface and that of the host.

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.

What is the function of reverse transcriptase in retroviruses?

B) It uses viral RNA as a template for DNA synthesis.

Why do RNA viruses appear to have higher rates of mutation?

B) Replication of their genomes does not involve the proofreading steps of DNA replication.

Which of the following describes plant virus infections?

B) They are spread throughout a plant by passing through the plasmodesmata.

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

B) Viruses have capsids composed of protein, whereas viroids have no capsids.

Viral envelopes can best be analyzed with which of the following techniques?

B) antibodies against specific proteins not found in the host membranes

SQ - RNA viruses require their own supply of certain enzymes because

B) host cells lack enzymes that can replicate the viral genome.

Antiviral drugs that have become useful are usually associated with which of the following properties?

B) interference with the viral reproduction

In 1971, David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA. The table below shows the results of testing five viruses for nuclease specificity, the ability of the virus to act as an mRNA, and presence (+) or absence (-) of its own viral polymerase. (refer to table) Given Baltimore's scheme, a positive sense single-stranded RNA virus such as the polio virus would be most closely related to which of the following?

B) retroviruses that require a DNA intermediate

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.

You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope III. culturing the substance by itself on nutritive medium, away from any plant cells IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious 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 describes the lysogenic cycle of lambda (λ) phage?

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

SQ - To cause a human pandemic, the H5N1 avian flu virus would have to

C) become capable of human-to-human transmission.

In many ways, the regulation of the genes of a particular group of viruses will be similar to the regulation of the host genes. Therefore, which of the following would you expect of the genes of the bacteriophage?

C) control of more than one gene in an operon

SQ - Which of the following characteristics, structures, or processes is common to both bacteria and viruses?

C) genetic material composed of nucleic acid

Which of the following terms describes bacteriophage DNA that has become integrated into the host cell chromosome?

C) prophages

In 1971, David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA. The table below shows the results of testing five viruses for nuclease specificity, the ability of the virus to act as an mRNA, and presence (+) or absence (-) of its own viral polymerase. (refer to table) Based on the above table, which virus meets the Baltimore requirements for a retrovirus?

D

Which of the following is characteristic of the lytic cycle?

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

You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope III. culturing the substance by itself on nutritive medium, away from any plant cells IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious Which treatment would you use to determine if the agent is a prion?

D) IV only

SQ - Emerging viruses arise by

D) all of the above (mutation of existing viruses, the spread of existing viruses to new host species, the spread of existing viruses more widely within their host species)

Which of the following accounts for someone who has had a herpesvirus-mediated cold sore or genital sore getting flare-ups for the rest of life?

D) copies of the herpesvirus genome permanently maintained in host nuclei

Viral genomes vary greatly in size and may include from four genes to several hundred genes. Which of the following viral features is most apt to correlate with the size of the genome?

D) size and shape of the capsid

Which of the following series best reflects what we know about how the flu virus moves between species?

E) An animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates and is passed to a new species such as a bird, the virus mutates and can be transmitted to humans.

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.

Which of the following is the most probable fate of a newly emerging virus that causes high mortality in its host?

E) The newly emerging virus will die out rather quickly or will mutate to be far less lethal.