VIRUSES

Which of the following statements is true regarding viruses? Because they are relatively complex in structure, they display remarkable diversity among species and strains. Although they are relatively complex in structure, they display little diversity among species and strains. Although they are simple in structure, they display remarkable diversity among species and strains Because they are simple in structure, they display little diversity among species and strains.

Although they are simple in structure, they display remarkable diversity among species and strains

How is an enveloped virus structurally different from a phage, like T4? An enveloped virus has a protein capsid, but a phage lacks a protein capsid. An enveloped virus has DNA as its genetic material, but a phage has RNA as its genetic material. The entire enveloped virus enter the cell by fusing with the plasma membrane, and phage inject their DNA into its host cell leaving its 'body' outside the cell. Enveloped virus possess an additional membrane around their protein capsid, phage do not possess a membrane.

Enveloped virus possess an additional membrane around their protein capsid, phage do not possess a membrane.

How is an enveloped virus structurally different from a phage, like T4?

Enveloped virus possess an additional membrane around their protein capsid, phage do not possess a membrane. (not multplechoice)

What must occur to end the lysogenic cycle? Excision of phage DNA Integration of phage DNA Excision of phage RNA Integration of phage RNA

Excision of phage DNA

In enveloped viruses, the viral envelope is composed of which of the following (choose all that apply)? Glycolipids Lipids Nucleoproteins Glycoproteins Lipoproteins

Lipids Glycoproteins

OMO Upon entry of the viral genome into the host cell, the viral nucleic acid molecule is destroyed by the host's immune defenses a few viral genes are turned off to avoid detection by the host cell a few viral genes are expressed using the host's molecular machinery the viral nucleic acid molecule is replicated by virus-encoded enzymes

a few viral genes are expressed using the host's molecular machinery

Upon entry of the viral genome into the host cell,

a few viral genes are expressed using the host's molecular machinery

Plasmids

are small, circular DNA molecules that exist independently of chromosomal DNA.

The viral envelope consists of a lipid _______ that is derived from a cellular membrane of the host cell and is embedded with virally-encoded spike _______.

bilayer ; glycoproteins

Temperate phages undergo:

both lytic and lysogenic cycles

In the second stage of HIV assembly, the newly formed capsid acquires its outer envelope by being released from the plasma membrane via a process called

budding

Capsids are composed of one or several different protein subunits called

capsomer

During step 4 of the phage reproductive cycle, the expression of phage genes also leads to the degradation of the ______ of the host.

chromosomal DNA

During attachment of HIV, the viral ______ fuses with the ______ of the host cell, so both the capsid and its contents are released into the cytoplasm.

envelope; cell membrane

The removal of the prophage from the bacterial chromosome is accomplished by the enzyme

excisionase

A species that can be infected by a specific virus is called a(n) _______ species for that virus.

host

To replicate, a virus or its genetic material must be in a living .

host

Antiviral drugs:

inhibit viral proliferation inside host cells

The enzyme _________ cuts the host's chromosomal DNA and inserts the viral genome into the chromosome.

integrase

The enzyme that enables a viral genome to be inserted into the chromosome of the host cell is called:

integrase

If the DNA of the provirus is transcribed

one long polygenic mRNA is produced.

Many bacteria possess small, circular DNA molecules that exist independently of the chromosomal DNA. These are called

plasmids

What is the function of the capsid and envelope in viruses? protect genetic material weaken host immune defenses enable host infection release genetic material encase genetic material replicate genetic material

protect genetic material enable host infection encase genetic material

In step 4 of the HIV reproductive cycle, _____ aDNA is not excised from the host chromosome. Instead, it is transcribed in the nucleus to produce many copies of viral RNA.

provirus

The viral DNA in a eukaryotic cell, once integrated, is called a(n)

provirus

A virus or its genetic material must be in a living host to ____

replicate

Viruses that have an RNA genome and carry the enzyme reverse transcriptase are collectively called .

retroviruses

What enzyme carried by HIV can copy the viral RNA genome into complementary DNA?

reverse transcriptase

How can the genetic information of retroviruses be characterized?

two copies of single-stranded RNA.

After HIV enters the cell, some of the HIV capsid proteins are then removed by host cell enzymes, a process called

uncoating

What do many viruses that infect animal cells have that surrounds the capsid?

viral envelope

The series of steps that result in the production of new viruses is BEST described as the:

viral reproductive system

A ____ is a small infectious particle composed primarily of RNA without a protein coat. A _____ is composed primarily of protein

viroid, prion

Which of the following describes a virus? A small infectious particle comprised of nucleic acid enclosed in a protein coat A small infectious particle that is comprised entirely of single-stranded, circular RNA A non-infectious cell with a complex structure that includes cytoplasm, nucleic acid, ribosomes, and peptidoglycan A small infectious particle that is comprised almost entirely of protein

A small infectious particle comprised of nucleic acid enclosed in a protein coat

What are prions?

Protein molecules that infect animal cells

Viruses that have an RNA genome and carry the enzyme reverse transcriptase are collectively called

RETROVIRUS