Virus

phages 2 reproductive mechanisms

- The lytic cycle - The lysogenic cycle

Which of the following events stimulates the production of viral particles in a host cell?

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

True

An animal virus with an envelope uses it to enter the host cell The envelope is made up from the plasma membrane

Virus

An infectious particle consisting of nucleic acid enclosed in a protein coat

Why do RNA viruses tend to have unusually high rates of mutation?

Replication of their genomes does not involve proofreading.

viral envelope

Surround the caspids of influenza viruses and many other viruses found in animals, derived from the host cell's membrane, contain a combination of viral and host cell molecules

A researcher lyses a cell that contains nucleic acid molecules and capsomeres 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 statements correctly describes one difference between vertical and horizontal transmission of plant viruses

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

Most molecular biologists think that viruses originated from naked bits of cellular nucleic acid. Which of the following observations supports this theory?

Viral genomes are usually similar to the genome of the host cell.

Which of the following statements accurately describes plant virus infections?

They are spread via the plasmodesmata

lytic cycle

a phage reproductive cycle that culminates in the death of the host cell - produced new phages and lyses the host's cell Wall,releasing the progeny viruses - A phage reproduces only by the lytic cycle is called a virulent phage - A bacteria have defenses against phages including restriction enzymes that recognize and cut up certain phage DNA

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

getting vaccinated

lysogenic cycle

replicates the phage genome without destroying the host - The viral DNA molecule is incorporated into the host cell's molecule -This integrated viral DNA is known as a prophage -Every time the host divides, it copies the phage DNA and passes the copies the phage DNA and passes the copies to daughter cells

The lytic cycle of bacteriophage infection ends with the

rupture of the bacterium

Which of the following statements correctly describes one characteristic of the lytic cycle of viral replication

A large number of phages are released at a time.

Bacteriaphage

Called phages Are viruses that infect bacteria

CRISPR-CAS

Consists of clustered regularly inter spaced short palindromic repeats and nucleares enzyme called CAS, CRISPR associated proteins

True

Each virus has a host range, a limited number that it can infect

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

How does HIV cause disease

HIV kills cells that defend the body against disease.

Which enzyme inserts viral DNA into the host's chromosomal DNA

Integrase inserts viral DNA into the host's chromosomal DNA.

What happens first when a phage infects a bacterial cell and is going to enter a lysogenic cycle

Linear DNA circularizes.

Which replicative cycle describes a virus that can integrate its genome into the host cell's genome

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

Virus Genomes

May consisting of either - Double or single-stranded DNA - Double or single-stranded RNA

True

Phage DNA is often identified as foreign and cut up as restriction enzymes

Temperate Changes

Phages that use both lytic and lysogenic cycles

Caspid

The protein shell that encloses that viral genome Built from protein subunits capsomeres

True

The viral envelope mediates entry into the cell, the capsid enters into the nuclear membrane, and the genome is all that enters the nucleus.

How does HIV bind to a host cell

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

How do enveloped viruses differ from nonenveloped viruses

They have a membrane-like outer covering.

Which of the following statements correctly describes the best predictor of how much damage a virus causes

ability of the infected cell to undergo normal cell division

Antiviral drugs that have become useful are usually associated with which of the following properties

interference with viral replication

HIV uses which of the following processes to synthesize a DNA strand using its RNA genome as a template

reverse transcription Retroviruses are equipped with an enzyme called reverse transcriptase, which makes a DNA copy of an RNA template, providing information flow from RNA to DNA.

As a result of the lytic cycle

the host cell's DNA is destroyed

Retroviruses

use reverse transcriptase to copy their RNA genome into DNA

In the lysogenic cycle

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