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26 Cards in this Set

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Virus
Structure
A virion is a complete, fully developed infectious viral particle cokmposed of nucleic acid and surrounded by a protein coat that protects it form the env. and is a vehicle of transmission from one host cell to another.
Nucleic Acid
Viruses contain either DNA or RNA, never both, and the nucleic acid may be single or double stranded, linear or circular or divided in several separate molecules.
The proportion of nucleic acid in relation to protein in viruses ranges from about 1%TO 50%.
Capsid
Protein coat surrounding the nucleic acid of a virus.
Capsid
Composed of subunits, capsomeres, which can be a single type of protein or several types
Envelope of Capsid
Covered with carbohydrate-protein complexes called spikes.
Multiplication of viruses
a. lytic Cycle
During a lytic cycle a phage causes the lysis and death of a host cell.
b. Lysogenic cycle
During the lysogenic cycle, prophage genes are regulated by a repressor coded for by the prophage. The prophage is replicated each time the cell divides.
A phage is a virus that infects bacterial cells.
A lysogenic phage can transfer bacterial genes from one cell to another through transduction. Any genes can be transferred in generalized transdujction, and specific genes can be transferred in specialized transduction.
c. Retroviruses
Or reoviridae are found in the respiratory and enteric (digestive) systems of humans. Reoviridae are digested in host cell cytoplasm to release mRNA for viral biosynthesis.
Retroviridae reverse transcriptase (RNA dependent DNA polymerase, transcribes DNA from RNA.
after maturation viruses are released. One method of release is budding. Naked viruses are released through ruptures in the host cell membrane.
Effects of viruses on cells
a. Isolation and detection of viruses
Viruses must be grown in living cells.
The easiest viruses to grow are bacteriophages. A virus that infects bacterial cells.
Growing bacteriophages in the lab
the plaque method mixes bacteriphages with host bacteria and nutrient agar.
After several viral multiplaction cycles, the bacteria in the area surrounding the original virus are destroyed; the area of lysis is called a plaque.
each plaque originates with a single viral particle; the concentration of viruses is given as plaque forming units.
fIdentification of viruses
Serological tests are used.,
Viruses may be identified by RFLPs and PCR.
Viral Multiplication
Viruses do not contain enzymes for energy production or protein synthesis.
For a virus to multiply, it must invade a host cell and direct the host's metabolic machinery to produce viral enzymes and components.
Multiplication of Bacteriophages(virus that infects bacterial cells)
During a lytic cycle, a phage causes the lysis and death of a host cell.
Some viruses can either cause lysis or have their dna incorporated as a prophage into the DNA of the host cell. the latter situation is call lysogeny.
The T-even bacteriophages taht infect E. coli have been studied extensively.
During attachmnent phase of the lytic cycle, site on the phages tail fibers attach to complimentary receptor sites on the bacterial cell.
In penetration phage lysozyme opens a portion of the bacterial cell wall, the tail sheath contracts to force the tail core through the cell wall, and phage dna enters bacterial cell. the capsid remains outside.
Virus
Structure
A virion is a complete, fully developed infectious viral particle cokmposed of nucleic acid and surrounded by a protein coat that protects it form the env. and is a vehicle of transmission from one host cell to another.
Nucleic Acid
Viruses contain either DNA or RNA, never both, and the nucleic acid may be single or double stranded, linear or circular or divided in several separate molecules.
The proportion of nucleic acid in relation to protein in viruses ranges from about 1%TO 50%.
Capsid
Protein coat surrounding the nucleic acid of a virus.
Capsid
Composed of subunits, capsomeres, which can be a single type of protein or several types
Envelope of Capsid
Covered with carbohydrate-protein complexes called spikes.
Multiplication of viruses
a. lytic Cycle
During a lytic cycle a phage causes the lysis and death of a host cell.
b. Lysogenic cycle
During the lysogenic cycle, prophage genes are regulated by a repressor coded for by the prophage. The prophage is replicated each time the cell divides.
A phage is a virus that infects bacterial cells.
A lysogenic phage can transfer bacterial genes from one cell to another through transduction. Any genes can be transferred in generalized transdujction, and specific genes can be transferred in specialized transduction.
c. Retroviruses
Or reoviridae are found in the respiratory and enteric (digestive) systems of humans. Reoviridae are digested in host cell cytoplasm to release mRNA for viral biosynthesis.
Retroviridae reverse transcriptase (RNA dependent DNA polymerase, transcribes DNA from RNA.
after maturation viruses are released. One method of release is budding. Naked viruses are released through ruptures in the host cell membrane.
Effects of viruses on cells
a. Isolation and detection of viruses
Viruses must be grown in living cells.
The easiest viruses to grow are bacteriophages. A virus that infects bacterial cells.
Growing bacteriophages in the lab
the plaque method mixes bacteriphages with host bacteria and nutrient agar.
After several viral multiplaction cycles, the bacteria in the area surrounding the original virus are destroyed; the area of lysis is called a plaque.
each plaque originates with a single viral particle; the concentration of viruses is given as plaque forming units.
fIdentification of viruses
Serological tests are used.,
Viruses may be identified by RFLPs and PCR.
Viral Multiplication
Viruses do not contain enzymes for energy production or protein synthesis.
For a virus to multiply, it must invade a host cell and direct the host's metabolic machinery to produce viral enzymes and components.
Multiplication of Bacteriophages(virus that infects bacterial cells)
During a lytic cycle, a phage causes the lysis and death of a host cell.
Some viruses can either cause lysis or have their dna incorporated as a prophage into the DNA of the host cell. the latter situation is call lysogeny.
The T-even bacteriophages taht infect E. coli have been studied extensively.
During attachmnent phase of the lytic cycle, site on the phages tail fibers attach to complimentary receptor sites on the bacterial cell.
In penetration phage lysozyme opens a portion of the bacterial cell wall, the tail sheath contracts to force the tail core through the cell wall, and phage dna enters bacterial cell. the capsid remains outside.