AP Bio Ch 19

Which of the following is characteristic of the lytic cycle? Viral DNA is incorporated into the host genome. A large number of phages are released at a time. The virus-host relationship usually lasts for generations. The viral genome replicates without destroying the host.

A large number of phages are released at a time.

Why are viruses called obligate intracellular parasites? They must use a host cell's amino acids to synthesize proteins. They must use a host cell's nucleotides for transcription and replication. They must use a host cell's ribosomes to synthesize proteins. They must use a host cell's metabolic enzymes and pathways to obtain energy. All of the above.

All of the above.

You are an epidemiologist for the Centers for Disease Control, specializing in schistosomiasis. Your goal is to reduce or eliminate this disease by focusing on the intermediate host. What are you researching?

Freshwater snail

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

Getting vaccinated

Will treating a viral infection with antibiotics affect the course of the infection? No; antibiotics do not kill viruses because viruses do not have DNA or RNA. Yes; antibiotics can prevent viral entry into the cell by binding to host-receptor proteins. Yes; antibiotics activate the immune system, and this decreases the severity of the infection. No; antibiotics work by inhibiting enzymes specific to bacteria. Antibiotics have no effect on eukaryotic or virally encoded enzymes.

No; antibiotics work by inhibiting enzymes specific to bacteria. Antibiotics have no effect on eukaryotic or virally encoded enzymes.

The H1N1 2009 outbreak is considered to have been which of the following?

Pandemic

How do prions, which are misfolded proteins, infect organisms? Prions enter brain cells and cause normal forms of the protein to refold into the prion form. Prions only arise through spontaneous mutation. They are not transmissible. Prions recruit ribosomes to make more copies of the wrong form of the protein. Prions enter brain cells through the lymphatic system and make copies of themselves. None of the above.

Prions enter brain cells and cause normal forms of the protein to refold into the prion form.

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

Replication of their genomes does not involve proofreading.

Which of the three types of viruses shown above would you expect to include glycoproteins?

1 and 2 only (not phage)

Which of the three types of viruses shown above would you expect to include a capsid(s)?

1, 2, 3

Which of the following represents a difference between viruses and viroids? Which of the following represents a difference between viruses and viroids? A) Viruses infect many types of cells, whereas viroids infect only prokaryotic cells. B) Viruses have capsids composed of protein, whereas viroids have no capsids. C) Viruses have genomes composed of RNA, whereas viroids have genomes composed of DNA. D) Viruses cannot pass through plasmodesmata, whereas viroids can.

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

Viral infections in plants _____. A) can be controlled with antibiotics B) can spread within a plant via plasmodesmata C) have little effect on plant growth D) are not spread by animals

B) can spread within a plant via plasmodesmata

You inhale the virus for the common cold. What sentinel cells does your immune system send out to determine the location of the infection?

CD4

What is the main structural difference between enveloped and nonenveloped viruses? Nonenveloped viruses have only a phospholipid membrane, while enveloped viruses have two membranes, the other one being a protein capsid. Enveloped viruses have their genetic material enclosed by a layer made only of protein. Both types of viruses have a capsid and phospholipid membrane; but in the nonenveloped virus the genetic material is between these two membranes, while in the enveloped virus the genetic material is inside both membranes. Enveloped viruses have a phospholipid membrane outside their capsid, whereas nonenveloped viruses do not have a phospholipid membrane.

Enveloped viruses have a phospholipid membrane outside their capsid, whereas nonenveloped viruses do not have a phospholipid membrane.

What is the function of reverse transcriptase? It catalyzes the formation of a polypeptide from an RNA template. It catalyzes the formation of DNA from a polypeptide template. It catalyzes the formation of RNA from a polypeptide template. It catalyzes the formation of RNA from a DNA template. It catalyzes the formation of DNA from a RNA template.

It catalyzes the formation of DNA from a RNA template

What is the function of reverse transcriptase in retroviruses?

It uses viral RNA as a template for DNA synthesis

bacterium-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

T4 protein and T4 DNA.

Which of the following statements describes the lysogenic cycle of lambda (λ) phage? The phage genome replicates along with the host genome. Most of the prophage genes are activated by the product of a particular prophage gene. The phage DNA is copied and exits the cell as a phage. After infection, the viral genes immediately turn the host cell into a lambda-producing factory, and the host cell then lyses.

The phage genome replicates along with the host genome.

A plant that has been raised in a sterile environment shows symptoms of a viral infection. How would you explain this? The viral infection was acquired by horizontal transmission. A group of plant genes mutated to become a viral genome. The viral infection was acquired by vertical transmission. A plant raised in a sterile environment cannot show symptoms of viral infection. The viral infection was acquired from the environment.

The viral infection was acquired by vertical transmission.

Which of the following supports the argument that viruses are nonliving? They have RNA rather than DNA. They do not evolve. They are not cellular. Their DNA does not encode proteins.

They are not cellular.

Why are retroviruses considered a special class of viruses? They leave behind mini-chromosomes when they leave a cell. They carry their own RNA-RNA synthesis enzymes inside their capsids. They have an RNA genome. They transcribe RNA to DNA using reverse transcriptase. They have a phospholipids membrane cloak.

They transcribe RNA to DNA using reverse transcriptase.

How do prions differ from viruses? Unlike viruses, prions are infectious proteins. Unlike a virus, a prion is a single molecule. Unlike viruses, prions do not include any nucleic acids.

Unlike viruses, prions are infectious proteins. Unlike a virus, a prion is a single molecule. Unlike viruses, prions do not include any nucleic acids.

Identify all correct statements about how viroids differ from viruses. Unlike viruses, viroids cause plant disease. Unlike viruses, viroids do not encode proteins. Unlike viruses, the genetic material of a viroid is protein.

Unlike viruses, viroids do not encode proteins.

How does a virus differ from a bacterium? A virus, unlike a bacterium, lacks a genome. Viruses are two-dimensional, whereas bacteria are three-dimensional. Viruses, unlike bacteria, lack metabolic enzymes.

Viruses, unlike bacteria, lack metabolic enzymes

All of the statements below are true. Select the statement that best supports the view of most biologists that viruses are nonliving. a) An isolated virus is unable to repolicate it's genes or regenerates ATP b) Viruses are obligate intracellular parasites. c) The viral genome may be single-stranded or double-stranded RNA or DNA

a) An isolated virus is unable to replicate it's genes or regenerates ATP

The host range of a virus is determined by _____. A. The proteins on its surface and that of the host. B. The proteins in the host s cytoplasm. C. Whether its nucleic acid is DNA or RNA. D. The enzymes carried by the virus. E. The enzymes produced by the virus before it infects the cell.

a. The proteins on its surface and that of the host.

Emerging viruses arise by the spread of existing viruses more widely within their host species. mutation of existing viruses. the spread of existing viruses to new host species. all of the above none of the above

all of the above

To cause a human pandemic, the H5N1 avian flu virus would have to develop into a virus with a different host range. arise independently in chickens in North and South America. become much more pathogenic. become capable of human-to-human transmission. spread to primates such as chimpanzees.

become capable of human-to-human transmission.

Why is it ineffective to treat viral disease with antibiotics? a) Pathogenic RNA viruses have a high rate of mutation, producing new genetic varieties that are insensitive to antibiotic treatment b) Due to excessive antibiotic use, most viruses have evolved to be resistant to antibiotics. c) Antibiotics inhibit enzymes specific to bacteria and have no effect on virally encoded enzymes.

c) Antibiotics inhibit enzymes specific to bacteria and have no effect on virally encoded enzymes.

A person is most likely to recover from a viral infection if the infected cells _____. can undergo normal cell division produce and release viral protein transcribe viral mRNA can carry on translation, at least for a few hours

can undergo normal cell division

The nucleic acid of a virus particle is enclosed in a protein coat. What is it called? envelope nuclear envelope capsid genome nucleoid

capsid

Which of the following accounts for someone who has had regular herpesvirus-mediated cold sore or genital sore flare-ups? re-infection by a closely related herpesvirus of a different strain copies of the herpesvirus genome permanently maintained in host nuclei copies of the herpesvirus genome permanently maintained in host cell cytoplasm re-infection by the same herpesvirus strain

copies of the herpesvirus genome permanently maintained in the host nuclei.

In the lysogenic cycle a. viral DNA is destroyed and host DNA is replicated. b. host DNA is destroyed and viral DNA is replicated. c. a bacterium divides once before the lytic cycle is initiated. d. viral DNA is replicated along with host DNA. e. a bacterium replicates without passing viral DNA to its daughter cells.

d. viral DNA is replicated along with host DNA.

The lytic cycle of bacteriophage infection ends with the a. assembly of viral particles into phages. b. replication of viral DNA. c. the injection of phage DNA into a bacterium. d. entry of the phage protein coat into the host cell. e. rupture of the bacterium.

e. rupture of the bacterium.

Which of the following characteristics, structures, or processes is common to both bacteria and viruses? cell division ribosomes independent existence genetic material composed of nucleic acid metabolism

genetic material composed of nucleic acid

In the figure, at the arrow marked II, what enzyme(s) are being utilized?

host cell DNA polymerase

What is the source of a viral envelope? host cell DNA prophages provirus host cell membrane viral glycoproteins

host cell membrane

RNA viruses require their own supply of certain enzymes because these enzymes penetrate host cell membranes. these enzymes translate viral mRNA into proteins. these enzymes cannot be made in host cells. host cells lack enzymes that can replicate the viral genome. host cells rapidly destroy the viruses.

host cells lack enzymes that can replicate the viral genome

Effective antiviral drugs are usually associated with which of the following properties? removal of viral proteins prevention of the host from becoming infected interference with viral replication removal of viral mRNAs

interference with viral replication

What happens first when a phage infects a bacterial cell and is going to enter a lysogenic cycle? All bacterial descendants will carry the viral genes. When the bacterial chromosome replicates, viral DNA is also replicated. Linear DNA circularizes. The host cell is lysed by the invasion. Viral DNA becomes inserted into the bacterial chromosome.

linear DNA circularizes

What are prions?

misfolded versions of normal protein that can cause disease

To make a vaccine against mumps, measles, or rabies, which type of viruses would be useful? sDNA viruses positive-sense ssRNA viruses dsRNA viruses negative-sense ssRNA viruses

negative-sense ssRNA viruses

In the figure, when new viruses are being assembled at the point marked IV, what mediates the assembly?

nothing; they self assemble

What do we call a virus that attacks a bacterium? phage prion viroid paramyxovirus retrovirus

phage

Double-stranded viral DNA is incorporated into a host cell as a _____. promoter provirus transposon lac homeoboxes

provirus ("Provirus" is the name given to double-stranded viral DNA that has been incorporated into a host cell's genome.)

A virus consisting of a single strand of RNA, which is transcribed into complementary DNA, is a _____.

retrovirus

Which viruses have single-stranded RNA that acts as a template for DNA synthesis?

retroviruses

HIV uses which of the following processes to synthesize a DNA strand using its RNA genome as a template? reverse transcription transcription conjugation translation reverse translation

reverse transcription

The genetic material of HIV consists of _____.

single stranded RNA

Which of the following could use reverse transcriptase to transcribe its genome?

ss RNA

As a result of the lytic cycle, _____. the host cell is not destroyed the host cell's DNA is destroyed viral ribosomes are produced viral DNA is incorporated into host cell DNA a prophage is created

the host cell's DNA is destroyed

The difference between vertical and horizontal transmission of plant viruses is that vertical transmission is _____. the spread of viruses from upper leaves to lower leaves of the plant, and horizontal transmission is the spread of a virus among leaves at the same general level the spread of viruses from trees and tall plants to bushes and other smaller plants, and horizontal transmission is the spread of viruses among plants of similar size the transfer of DNA from a plant of one species to a plant of a different species, and horizontal transmission is the spread of viruses among plants of the same species transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant

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

Viruses _____. use the host cell to copy themselves and then viruses synthesize their own proteins manufacture their own ATP, proteins, and nucleic acids metabolize food and produce their own ATP use the host cell to copy themselves and make viral proteins

use the host cell to copy themselves and make viral proteins

What is the most effective way to stop viral infections?

vaccines