Complex viruses: - CORRECT ANSWER-Example: poxviruses - DNA
surrounded by layers of lipoproteins
Example: T4 Bacteriophage - DNA or RNA surrounded by capsid, helical protein
tail, tail fibers
Classifications: International Committee on the Taxonomy of Viruses (ICTV) -
CORRECT ANSWER-1.) Nucleic acid type (single-stranded or double-stranded
DNA; single-stranded or double-stranded RNA)
2.) Replication process
3.) Morphology (envelope, capsid type, etc.)
4.) Effects
Viral host range - CORRECT ANSWER-Types of cells within a host species
which can be infected by the virus
Determined by attachment (susceptible) and cellular components necessary for
viral replication processes (permissive).
Bacteriophage multiplication: - CORRECT ANSWER-1.) Attachment - phage
attaches to host cell.
2.) Penetration - phage penetrates host cell and injects its DNA.
3.) Biosynthesis - phage DNA directs synthesis of viral components by the host
cell.
4.) Maturation - viral components are assembled into virions
5.) Release - host cell lyses and new virions are released.
Animal viruses - CORRECT ANSWER-Variations on the same 5 basic viral
multiplication steps based on:
Genetic material
Surface structures
Enzymes of virus and/or host cell
DNA animal virus - CORRECT ANSWER-1.) Virion attaches to host cell.
2.) Virion enters cell, and its DNA is uncoated
3.) A portion of viral DNA is transcribed, producing mRNA that encodes "early"
viral proteins.
4.) Viral DNA is replicated, and some viral proteins are made.
5.) Late translation; capsid proteins are synthesized.
6.) Virions mature.
7.) Virions released.
RNA viral multiplication (ssRNA; + or sense strand; Picornaviridae) - CORRECT
ANSWER-1.) Attachment
,2.) Entry and uncoating. Uncoating releases viral RNA and proteins.
3.) RNA replication by viral RNA-dependent RNA polymerase. - strand is
transcribed from + viral genome. mRNA is transcribed from the - strand.
4.) Translation and synthesis of viral proteins.
5.) Maturation and release.
RNA viral multiplication (ssRNA; - or antisense strand; Rhabdoviridae -
CORRECT ANSWER-1.) Attachment.
2.) Entry and uncoating. Uncoating releases viral RNA and proteins.
3.) RNA replication by viral RNA-dependent RNA polymerase. The + strand
(mRNA) must first be transcribed from the - viral genome before proteins can be
synthesized. Additional - strands are transcribed from mRNA.
4.) Translation and synthesis of viral proteins. - strands are incorporated into
capsid.
5.) Maturation and release
RNA viral multiplication (dsRNA; + or sense strand with - or antisense strand,
Reoviridae - CORRECT ANSWER-1.) Attachment
2.) Entry and uncoating. Uncoating releases viral RNA and proteins.
3.) RNA replication by viral RNA-dependent RNA polymerase. mRNA is
produced inside the capsid and released into the cytoplasm of the host.
4.) Translation and synthesis of viral proteins. RNA polymerase initiates
production of - strands. The mRNA and - strands form the dsRNA that is
incorporated as new viral genome.
5.) Maturation and release.
1.) Retrovirus enters by fusion between attachment spikes and the host cell
receptors.
2.) Uncoating releases the two viral RNA genomes and the viral enzymes
reverse transcriptase, integrase, and protease.
3.) Reverse transcriptase copies viral RNA to produce double-stranded DNA.
4.) The new viral DNA is transported into the host cell's nucleus, where it is
integrated into a host cell chromosome as a provirus by viral integrase. The
provirus may be replicated when the host cell replicates.
, 5.) Transcription of the provirus may also occur, producing RNA for new
retrovirus genomes and RNA encodes the retrovirus capsid, enzymes, and
envelope proteins.
6.) Viral proteins are processed by viral protease; some of the viral proteins are
moved to the host plasma membrane.
7.) Mature retrovirus leaves the host cell, acquiring an envelope and attachment
spikes as it buds out.
Viruses that induce cancer - CORRECT ANSWER-Human papilloma viruses
(HPVs)
Adenoviruses
Epstein-Barr virus (EBV - commonly known as mono)
Pox viruses
Hepatitis B virus (HBV) and Hepatitis C virus (HCV)
Human herpes virus 8 (HHV-8)
Human T-lymphotrophic virus - 1 & 2 (HTLV - 1/2)
Acute infection - CORRECT ANSWER-Short, large number of virions when host
cell is invaded.
Example: influenza
Persistent/chronic infection - CORRECT ANSWER-Slow and long, increase in
number of virions over a long period of time.
Example: HIV
Viral induced cancer - CORRECT ANSWER-First discovered in chickens in the
early 1900's. Caused leukemia and sarcoma.
Accounts for up to 20% of all cancers in humans
Rouse-sarcoma virus - CORRECT ANSWER-Discovered by Rouse.
Oncogenes - CORRECT ANSWER-Genes which have the ability to induce
cancer if altered (mutated).
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