Bio Chapter 19.

HIV is the viral agent that causes ______.

AIDS

What is the function of reverse transcriptase in retroviruses? It hydrolyzes the host cell's DNA.

It uses viral RNA as a template for DNA synthesis.

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

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

A specific RNA virus follows a lysogenic life cycle. Which of the following is necessary for the survival of the virus in this particular life cycle? (MCAT)

Reverse transcriptase

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.

A researcher lyses a cell that contains nucleic acid molecules and capsid proteins 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?

The plants would develop the typical symptoms of TMV infection.

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

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

Why are viruses referred to as obligate parasites?

They cannot reproduce outside of a host cell.

(GRE) Which of the following is true concerning animal retroviruses?

They require an RNA-dependent DNA polymerase

retro (retrovirus)

backward, behind

Viruses that infect bacteria are ______.

bacteriophages

pan (pandemic)

all, every, whole

The ______________ cycle results in viral DNA being incorporated into the host bacterium's genome.

lysogenic

The _____________ cycle results in the release of thousands of viruses from a dead bacterial host.

lytic

RNA viruses require their own supply of certain enzymes because

host cells lack enzymes that can replicate the viral genome.

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

genetic material composed of nucleic acid

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

getting vaccinated

adeno (adenovirus)

gland

Which of the following molecules are found as part of viral envelopes?

glycoproteins

A vaccine against a virus with an envelope would work best if it heightened immune reactions against

glycoproteins not found in the host membrane

In plants, viruses can travel between cells through

plasmodesmata

(GRE) An infectious agent that appears to have no nucleic acid is a

prion

A(n) ____________ is an infectious, misfolded protein that can cause normal proteins to misfold.

prion

gen (lysogenic)

produce, create

The piece of viral DNA that has been incorporated into a bacterial genome is called a(n) ___________.

prophage

A(n) ______ is to bacteria as a ______ is to animal cells.

prophage . . . provirus

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

prophages

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?

rabies

Lysogenic viruses do not

reproduce and lyse the host cell immediately

icosa (icosahedral)

twenty

Which of the following is necessarily true for all viruses? (MCAT)

Contains a protein coat which stores genetic material

Why are emerging viruses especially dangerous?

Populations are susceptible because they have no immunity to them.

Cytomegalovirus is a type of herpes virus which easily infects people. The majority of people infected are unaware of the infection, and the virus integrates into the host genome and almost always lies dormant for the lifespan of the any infected patient. This information suggests which of the following regarding the population effects of cytomegalovirus? (MCAT)

The percentage of people infected with cytomegalovirus should be greater for the elderly than for children.

Which process involves transfer of DNA from a virus to a bacterium? (MCAT)

Transduction

The lytic viral life cycle involves the lysis of the host cell and the release of virus particles. In contrast, the lysogenic cycle involves the dormancy of a virus within its host. Given the persistent DNAse and RNAse degradation in the cell, which of the following viruses is most likely to be involved in a lysogenic cycle? (MCAT)

a virus which has integrated its genome into the host genome

The first thing you notice is that there is no immediate increase in viruses following infection. This is because ______.

although the virus has infected the host, it takes time to complete the lytic cycle

epi (epidemic)

among, upon

zoo (zoonosis)

animal

Glycoproteins allow a virus to...

attach to a host cell

The first step in infection of a host bacterial cells by a phage is

attachment

pro (prophage)

beforehand, in advance

lys, lyt (lytic)

break, loosen

The protein cover surrounding the genetic material of a virus is called the

capsid

The protein subunits of a viral capsid are called _______________.

capsomeres

Which of the following accounts for someone who has had herpesvirus-mediated cold sores getting flare-ups for the rest of their lives?

copies of the herpesvirus genome were permanently maintained in the host cell's nuclei.

phag (bacteriophage)

eat

ase (transcriptase)

enzyme

A(n) ________________ is a fairly local outbreak of infection from a pathogen.

epidemic

The HIV virus first affects the ______________ system of the body.

immune

What are prions?

misfolded versions of normal brain protein

dem (epidemic)

people, district

The piece of viral DNA that has been incorporated into a eukaryotic genome is called a(n) ___________.

provirus

A(n) ___________________________ is an RNA virus that can transcribe its RNA into DNA and insert that DNA into the host's genome.

retrovirus

HIV (human immunodeficiency virus) must use its own ______ to reproduce.

reverse transcriptase

Once viruses are detected, the number of viruses increases rapidly. This is because

the viruses lyse the hosts to release mature viruses all at once

How can bacteriophage DNA be spread from cell to cell without causing cell death?

via a lysogenic cycle

A(n) ______________ consists of a protein coat surrounding genetic material and little else.

virion ,virus

A(n) ______________ is an infectious piece of circular RNA that affects plants.

viroid

A(n) ___________________ _______________ is a virus that kills its host bacterium.

virulent phage