Micro 13 fill in the blank/ True false

According to The International Committee on the Taxonomy of Viruses (ICTV) scheme of classification, viruses can be classified by a variety of characteristics, including the diseases they cause. T/F

False According to the ICTV scheme of classification, viruses are classified only by their type of nucleic acid, presence of an envelope, shape, and size.

The destruction of chickens and other domesticated fowl prevents the spread of avian influenza. T/F

False Avian influenza viruses are not limited to domesticated fowl alone; they can also be found in wild birds, which can harbor and spread the disease

Diploid cell cultures have an unlimited life span. T/F

False Because diploid cell cultures are derived from normal cells (usually embryonic) and not tumor cells, they divide only about 100 times before they die.

Retroviruses need RNA-dependent RNA transcriptase to replicate themselves in the host cell. T/F

False Retroviruses use reverse transcriptase to make a DNA copy of their RNA genome, which is then used to transcribe the mRNA that will be used to produce the viral proteins

Bacteriophages outnumber all life forms. T/F

True Bacteriophages are more numerous than any cellular form of life. Think about the size of bacteriophages and their ability to be replicated.

Lysogenic bacteriophages are excised from the chromosome by any agent that damages the cell's DNA. T/F

True Recall that some inductive agents of a prophage are ultraviolet light, X-rays, and carcinogens. Inductive agents are typically agents that specifically damage the DNA of the cell.

Bacteriophages can be used in place of antibiotics to treat certain bacterial diseases. T/F

True This use of bacteriophages was explored in the early 1900s, and it may be useful today in the face of growing antibiotic resistance.

Proviruses become a permanent part of the host cell's genome. T/F

True Unlike lysogenic phages, animal viruses that engage in latency produce a provirus that becomes a permanent part of the host cell's genome. HIV is an example of a provirus.

Viruses have genomes of DNA or RNA but never both. T/F

True Viruses contain DNA or RNA but never both

Viruses can specifically infect one type of cell within an organism. T/F

True Viruses specifically infect only certain types of cell because of their interactions with molecules on the cell surface

The stage of the viral life cycle is usually a spontaneous process, although in some viruses it is controlled by enzymes.

assembly This stage involves the association of capsid proteins with nucleic acid molecules.

A(n) is a membrane that surrounds some viral capsids.

envelope viral envelope This structure is derived from the membranes of the cell.

The most common type of polyhedral capsid is a(n) .

icosahedron icosahedral capsid Viral morphology is based on capsid shape. This is a polyhedral capsid that has 20 sides.

A prophage is excised from the host chromosome and viral replication proceeds in a process called .

induction A prophage may remain inactive for generations. The excision can be provoked by agents that damage DNA molecules, such as X-rays.

The replication cycle in bacteriophages results in the death of the cell.

lytic This term refers to the destruction of something, such as a cell.

Tumors that invade neighboring tissues and travel throughout the body are exhibiting a phenomenon known as .

metastasis Tumors that are malignant are able to travel to different parts of the body and produce new tumors.

An infection in which a host cell sheds new viruses slowly and steadily is called a(n) infection.

persistent A single host cell may give rise to many virions. This type of infection is often associated with animal viruses, and it usually involves budding.

A technique used to estimate the numbers of bacteriophages in a culture is called a(n) assay.

plaque This technique involves counting areas of lysed cells on a bacterial lawn.

As a group, prion diseases are more formally known as (two words).

spongiform encephalopathies These diseases are characterized by the presence of large vacuoles in brain tissue, giving it the appearance of a sponge. Prion disease was observed as scrapie in sheep.

Small, circular RNA molecules that are infectious to plants are called .

viroids These infectious agents are similar to RNA viruses except that they lack capsids.