Chapter 19- Viruses

Which replicative cycle describes a virus that can integrate its genome into the host cell's genome? A. Lysogenic B. Mutagenic C. Viral D. Lytic

A. Lysogenic A lysogenic virus can integrate its genome into the host cell's genome and be duplicated by the host cell's replication machinery.

How do enveloped viruses differ from nonenveloped viruses? A. They have a membrane-like outer covering. B. They are too small to see with a light microscope. C. They have a capsid. D. They have a protein coat.

A. They have a membrane-like outer covering. Enveloped viruses have a membrane-like outer covering (an envelope) surrounding their capsid

Cycle A is the _____ cycle and cycle B is the _____ cycle. A. lytic ... lysogenic B. lytic ... phage C. lysogenic ... phage D. lysogenic ... lytic E. phage ... lysogenic

A. lytic ... lysogenic The lytic cycle concludes with rupture of the host cell. The lysogenic cycle involves replication of viral DNA along with replication of the host.

Select the four statements that are true. A. HIV contains two identical strands of DNA. B. A retrovirus contains RNA. C. HIV contains reverse transcriptase. D. All RNA-containing viruses are retroviruses. E.All viral genomes contain both DNA and RNA. F. The capsid enters the host cell if the virus is enveloped. G. Enveloped viruses bud from the host cell.

B. A retrovirus contains RNA. C. HIV contains reverse transcriptase. F. The capsid enters the host cell if the virus is enveloped. G. Enveloped viruses bud from the host cell.

Which enzyme inserts viral DNA into the host's chromosomal DNA? A. Protease B. Integrase C. DNA polymerase D. Reverse transcriptase

B. Integrase

Double-stranded viral DNA is incorporated into a host cell as a _____. A. promoter B. provirus C. transposon D. lac E. homeoboxes

B. provirus

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

B. the host cell's DNA is destroyed The host cell's DNA is destroyed, and ultimately, the host cell itself is destroyed in the lytic cycle.

What percentage of human DNA is viral DNA? A. 10% B. 64% C. 8% D. 76%

C. 8%

How does HIV cause disease? A. HIV mutates host DNA and causes cancer. B. HIV kills red blood cells. C. HIV kills cells that defend the body against disease. D. HIV kills brain cells.

C. HIV kills cells that defend the body against disease. HIV affects the immune system and kills cells that protect the body from foreign bacteria and viruses.

How does HIV bind to a host cell? A. CD4 binds to a co-receptor on the cell surface. B. CD4 binds to the viral capsid on the cell surface. C. The viral envelope proteins interact with CD4 and a co-receptor on the cell membrane. D. The viral envelope proteins interact with gp120 on the host-cell membrane.

C. The viral envelope proteins interact with CD4 and a co-receptor on the cell membrane.

Which of the following events stimulates the production of viral particles in a host cell? A. Low-level transcription of viral DNA. B. Assembly of viral proteins and mRNA molecules. C. Processing of viral envelope proteins at the Golgi. D. Activation of the host cell by cytokines, growth factors, or antigens.

D. Activation of the host cell by cytokines, growth factors, or antigens. Activation of the host immune cell by cytokines, growth factors, or antigens causes viral DNA to be transcribed at high rates in preparation for viral production.

What is the source of a viral envelope? A. host cell DNA B. prophages C. provirus D. host cell membrane E. viral glycoproteins

D. host cell membrane

What is the function of reverse transcriptase? A. It catalyzes the formation of a polypeptide from an RNA template. B. It catalyzes the formation of DNA from a polypeptide template. C. It catalyzes the formation of RNA from a polypeptide template. D. It catalyzes the formation of RNA from a DNA template. E. It catalyzes the formation of DNA from an RNA template.

E. It catalyzes the formation of DNA from an RNA template.

The lytic cycle of bacteriophage infection ends with the _____. A. replication of viral DNA B. entry of the phage protein coat into the host cell C.assembly of viral particles into phages D. the injection of phage DNA into a bacterium E. rupture of the bacterium

E. rupture of the bacterium The bacterium ruptures and phages are released.

In the lysogenic cycle _____. A. host DNA is destroyed and viral DNA is replicated B. a bacterium replicates without passing viral DNA to its daughter cells C. viral DNA is destroyed and host DNA is replicated D. a bacterium divides once before the lytic cycle is initiated E. viral DNA is replicated along with host DNA

E. viral DNA is replicated along with host DNA Viral DNA, incorporated into host DNA as a prophage, is replicated along with host DNA.

True or false? The human immunodeficiency virus (HIV) uses reverse transcriptase to make double-stranded RNA copies of its DNA genome.

False A retrovirus such as HIV has an RNA genome and uses reverse transcriptase to make double-stranded DNA copies of the genome, which can then be integrated into the host cell's genome.

True or False? Viruses can reproduce or carry out metabolism outside of a host cell.

False Viruses CANNOT reproduce or carry out metabolism outside of a host cell.

Classify each phrase as applying to the lytic cycle, the lysogenic cycle, or both types of reproductive cycles of phages. cell reproduces normally viral genes are replicated the host cell is destroyed the cell is lysed (broken open) new phages are assembled from viral DNA and proteins the viral DNA integrates into the chromosome of the host cell

LYTIC CYCLE the host cell is destroyed new phages are assembled from viral DNA and proteins the cell is lysed (broken open) LYSOGENIC CYCLE cell reproduces normally the viral DNA integrates into the chromosome of the host cell BOTH CYCLES viral genes are replicated

DNA or _________ functions as the genetic material in viruses.

RNA

True or False? A virus is called DNA or an RNA virus based on the type of nucleic acid.

True

True or False? Viral genomes may consist of either double- or single-stranded DNA or RNA.

True

Sort the items into the following categories: VIRUSES ONLY; HOST CELL ONLY; BOTH capsid ribosome DNA capsomere (core protein) envelope with glycoproteins protein RNA

VIRUSES ONLY capsid envelope with glycoproteins capsomere (core protein) HOST CELL ONLY ribosome BOTH protein DNA RNA

restriction enzymes

bacteria defense mechanism against phages; recognize and cut up certain phage DNA

A _______ is the shell that covers the nucleic acid of a virus.

capsid

A __________________ is a protein building block of a capsid

capsomere (core protein)

retroviruses

copies RNA genome into DNA with reverse transcriptase

A membrane called the ____________ surrounds the capsid in some viruses.

envelope

reverse transcriptase

enzyme that copies RNA genome into DNA

epidemic

general outbreak of a virus

pandemic

global epidemics

A ________________ is a protein with one or more carbohydrates attached to it that can bind to specific receptor molecules.

glycoprotein

vaccines

harmless derivatives of pathogenic microbes that stimulate the immune system to mount defenses against harmful pathogen

virus

infectious particle consisting of genes packaged in a protein coat and, in some cases, a membranous envelope

prophage

integrated viral DNA

host range

limited number of host cells a virus can infect

lytic cycle

phage replicative cycle that culminates in the death of a host cell

virulent phage

phage that reproduces only by the lytic cycle

temperate phages

phages that use both the lytic and lysogenic cycles

capsid

protein shell that encloses viral genome

capsomeres

protein subunits on a capsid

lysogenic cycle

replicates phage genome without destroying the host

HIV (human immunodeficiency virus)

retrovirus that causes AIDS (acquired immunodeficiency syndrome)

viral envelopes

surround capsids of influenza viruses and many other viruses found in animals

provirus

viral DNA integrated into host genome

emerging virus

virus that suddenly becomes apparent

bacteriophages (phages)

viruses that infect bacteria