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24 Cards in this Set

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Virus
-noncellular
-obligate (need host)
-intracellular
-parasites
-DNA or RNA
-No plasma membrane
-Cannot carry out transcription or translation
-No metabolic capabilities
-Single or double stranded
-Paricles or agents
Bacteriophage
viruses that infect bacteria
Viral diseases
-HIV/AIDS
-SARS
-West Nile
-Influenza
-Cold
-Spanish flu
-Etc.
HIV
Human Immunodeficiency Virus
-causes AIDS
-parasitizes and destroys helper T cells and macrophages
-T cell drops --> less able to fight infections
-enveloped
AIDS
Acquired Immune Deficiency Syndrome
-caused by HIV
-killed 25 million
-42 million infected
Viral Morphology
-very small
-vary in size and shape
-enveloped/noneveloped
What are the two types of viruses?
1. Noneveloped
2. Enveloped
Nonenveloped
-enclosed by just a shell of protein (capsid)
Enveloped
-Enclosed by capsid and membrane like enveloped
-HIV
What are the two ways a virus can infect its host cell?
1. Lytic
2. Lysogenic
Lytic Replication Cycle
-Viral particles are made and released from the cell, usually resulting in death of the host
1. Viral genome enters host
2. Viral genome is replicated and transcribed
3. Viral mRNAs are translated, and proteins produced
4. Particles assemble inside host
5. Particles exit to exterior
Lysogenic Replication Cycle
-Viral genes are incorporated in the host's chromosome and are transmitted to the host's daughter cells
1. Viral genome enters host
2. Viral genomes integrate into host cell genomes
3. Host-cell DNA polymerase copies chromosome
4. Cell divides. Virus is transmitted to daughter cells
How are viruses transmitted to new hosts?
-Budding of enveloped
-Bursting of noneveloped
Positve-sense viruses
Genome contains the same sequences as the mRNA required to produce viral proteins
Negative-sense viruses
Base sequences in genome are complementary to those in viral mRNAs
Ambisense virusees
Contain both positive and negative-sense sections
Where did viruses coem from?
1. Escaped-genes hypothesis
2. Degeneration hypothesis
Escaped-Genes Hypothesis
Viruses descended from clusters of genes that physically escaped from bacterial or eukaryotic chromosomes long ago
Degeneration Hypothesis
Organisms gradually degenerated into viruses by slowly losing the genes required to synthesize ATP and other compounds
Double-Stranded DNA (dsDNA) Viruses
-Smallpox, pox viruses, herpes, adenovirus
Girls with Double Ds get Herpes!
-Viral genes enter nucleus so they can infect only cells that are actively dividing
-Hosts include all types of organisms, except land plants
RNA Reverse-Transcribing Viruses (Retroviruses)
-Single-stranded RNA (two copies- diploid)
-Reverse transcriptase
-Parasitizes only vertebrates, birds, fish, or mammals
Double-Stranded RNA (dsRNA) Viruses
-Template for synthesis of viral RNAs, which are then translated into viral proteins
-Wide variety of hosts
-Crops
Negative-Sense Single-Stranded RNA ([-]ssRNA) Viruses
-RNA polymerease uses [-] sense template to make viral mRNAs, which are then translated to form viral proteins and new [-]ssRNA
-Many plant and animal hosts
-Flu, mumps, measles, Ebola, Hanta, Rabies (Mary)
Positive-Sense Single-Stranded RNA ([+]ssRNA) Viruses
-Plant viruses, mosaic viruses (Gary likes tobacco. It’s positive)
-Common cold, polio, hepatitis A, C, and E