Chapter 13 Microbiology

Membrane fusion

the viral envelope and the host membrane fuse releasing the capsid into the cell's cytoplasm and leaving the envelope glycoproteins as part of the cell membrane and uncoating happens

How do dsRNA viruses product new virus particles?

unwinds so that each strand serves as a template for its complement.

Nucleocapsid

the nucleic acid and its capsid

Induction

the process where a prophage is excised from the host chromosome

Bacteriophage

virus that infects bacteria

What are the steps of the lytic cycle?

1. attachment of the virion to the host cell 2. Entry of the virion or its genome into the host cell 3. Bacterial chromosome is degraded 4. Synthesis of new nucleic acids and viral proteins by the host cell's enzymes and ribosomes. 5. Assembly of new virions within the host cell 6. Release of the new virions from the host cell, as lysozyme completes its work on the cell wall and the bacterium disintegrates

What is a protooncogene?

A gene that could cause cancer if ti becomes activate

Prophage

An inactive bacteriophage, which is inserted into a host's chromosome.

Plaque

In phage typing, the clear region within the bacterial lawn where growth is inhibited by bacteriophages.

Provirus

Inactive virus in an animal cell inserted into the DNA of the host

What are the differences between provirus and prophage?

Provirus: inactive inside the DNA of an animal cell Prophage: inactive in bacteria

How do negative ssRNA viruses product new virus particles?

RNA dependent RNA transcriptase which is released into the host cells cytoplasm during uncoating and then transcribes +RNA molecules from the virus's -RNA genome. Translation of proteins can then occur as usual. The newly transcribed +RNA also serves as a template for transcription of additional copies of -RNA.

How are the lytic cycle and lysogeny related?

The first 2 steps are the same then the lysogenic cycle does 2 steps differently then the lytic cycle. Then the lytic cycle is reactivated for last 3 steps of the lytic cycle.

What are the similarities between provirus and prophage?

They are both inactive forms

What are the steps in the lysogenic cycle?

They follow the same first 2 steps of the lytic cycle - 3. the prophage is inserted into the DNA of the bacterium, becoming a physical part of the bacterial chromosome. 4. Every time the cell replicates its infected chromosome, the prophage is also replicated. 5. At some later time a prophage might be excised from the chromosome by recombination or some other genetic event - it reenters the lytic cycle. Then the rest follows the lytic cycle - synthesize, assembly, and release.

How do retroviruses differ from other +ssRNA viruses with regard to their production of new virus particles?

Unlike other +ssRNA viruses, the +ssRNA viruses called retroviruses do not use their genome as mRNA. Instead, retroviruses use a DNA intermediary that is transcribed from +RNA by reverse transcriptase carried within the capsid. This DNA intermediary then serves as the template for the synthesis of additional +RNA molecules which act both as mRNA for protein synthesis and as genomes for new virons

Envelope

a phospholipid membrane surrounding the nucleocapsid

Capsomers

a proteinaceous subunit of a capsid.

Virion

free viruses that need something to help them attach to infect the host

Uncoating

is the removal of a viral capsid within a host cell

Lysogenic Conversion

lysogenic phages can change the phenotype of a bacterium , for example from a harmless form into a pathogen

What would determine whether a prion disease can be transmitted across species?

prion would change normal proteins into prions

Latency

process by which an animal virus, sometimes not incorporated into the chromosomes of the cell, remain inactive in the cell, possibly for years.

Capsid

protein coat surrounding a nucleic acid core.

How do positive ssRNA viruses product new virus particles?

single stranded viral RNA that can directly act as mRNA. A complementary negative strand RNA is transcribed from the +ssRNA genome by viral RNA polymerase; -RNA then serves as the template for the transcription of multiple +ssRNA genomes.

Under what condition would a person be a carrier for a virus infection?

someone who is asymptomatic and there is replication of the virus

Budding

usually used for animal viruses with an envelope. Each virion acquires a portion of membrane which becomes the viral envelope. Naked animal viruses can also be released from the cell this way as well. Because the host cell is not quickly lysed, as occurs in bacteriophage replication, as allows an infected cell to remain alive for some time