Ch 24

Do viruses have a cytoplasm, mitochondria, and ribosomes?

no

proto-oncogene

Normal genes that promote cell division.

What is a vaccine?

A substance introduced into the body to stimulate the production of chemicals that destroy specific viruses or bacteria

lysogenic cycle

A viral reproductive cycle in which the viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA

retrovirus

A virus that enters a host cell and changes its RNA to a proviral DNA replica.

bacteriophage

A virus that infects bacteria

What allows viruses to spread so fast from country to country in modern times?

Air Travel

What is not a vector of viral diseases?

Prions

Scientists began to study viruses because they

could not be seen but caused diseases

Viruses reproduce

in only living cells

animal viruses often infect only specific host cells because

the host cell might have specific receptors for proteins on the virus surface

virulent

virus that replicates only by the lytic cycle

reverse transcriptase

- an enzyme that synthesize DNA instead of RN

lysis

- swelling of cells that eventually bursts, disintegration of cells

How does an RNA virus get viral DNA into a host cell's genome?

-RNA gets released into the host cell -RNA is transcripted into DNA by reverse transcriptase -DNA is integrated into the host cell's genome

envelope

A membranelike layer that covers the capsids of some viruses.

Virus

A nonliving, intracellular parasite. Viruses are typically just pieces of nucleic aid surrounded by a protein coat.

prophage

A phage genome that has been inserted into a specific site on the bacterial chromosome.

Viroid

A strand of RNA or DNA that lacks the protein capsid

vaccine

A substance prepared from killed or weakened pathogens and introduced into a body to produce immunity.

lytic cycle

A type of viral replication cycle resulting in the release of new viruses by lysis (breaking open) of the host cell.

Prions

An infectious form of protein that may multiply by converting related proteins to more prions

What describes what is happening

Bacteriophage attacking a bacterial cell

How does structure and function of bacteriophages make these viruses useful tools for genetic engineering?

Bacteriophages are very good at injecting foreign DNA into bacteria. Genetic Engineers use them to introduce DNA of interest to humans in bacteria

oncogenes

Cancer-causing genes that are formed due to mutations

protease inhibitors

HIV antiviral class known to have severe drug interactions by causing inhibition of metabolism

provirus

Integrated viral DNA

Why would a drug that blocks DNA transcription not be a desirable method for treating a viral disease?

It would block transcription of the host cell's genes as well as viral genes.

capsid

Outer protein coat of a virus

The instructions for making new copies of a virus are coded in

RNA or DNA

Viruses that contain RNA as their genetic material are called

Retroviruses

What substance does a retrovirus use to force their host cells to transcribe DNA form an RNA template

Reverse Transcriptase

Why must a person receive a different flu vaccination each year to be protected against the flu?

The flu virus mutates quickly making new strands - the flu vaccine targets a different strand every year

why are viruses not considered to be living organisms?

They do not have all the characteristics of life

What did Wendell Stanley's work suggest about the nature of viruses?

Viruses were chemicals rather than tiny cells

inactivated virus

a virus that is not able to replicate in a host.

temperate virus

a virus whose replication includes the lysogenic cycle

Attenuated Virus

a weakened form of the virus that cannot cause disease

Describe the structure of ABCD&E

a-protein coat b-RNA c-envelope d-glycoprotein e-reverse transcriptase

antibiotics are ineffective against viral infections because

antibiotics interfere in cellular processes that viruses do not preform

vector

any agent that can put foreign dna into something

A lyctic infection concludes with the

bursting of the host cell

The outer protein coat of a virus is called a

capsid

emerging disease

disease that appears in the population for the first time, or an old disease that suddenly becomes harder to control

unlike lyctic viruses, lysogenic viruses do not...

lyse the host cell right away

In which cell cycle does viral dna become integrated into the host cell's DNA

lysogenic

Name 4 viruses that can cause disease and can be fatal?

rabies, smallpox, HIV, and Ebola

What kind of factors can cause a prophage to become a virulent?

radiation and certain chemicals

If viruses aren't living, why are they studied in biology?

some scientists (biologists) believe that they are alive.