Viruses and Virology Overview

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Questions and Answers

Match the following viral components with their primary functions:

Glycoproteins = Bind to host cells for entry Nucleic acid = Contains the genetic information for viral replication Capsid = Protects the viral genome Enzymes = Carry out specific functions necessary for viral replication

Match the following viral mechanisms with their respective viral families:

Self-complementary sequences at the 5' end of the RNA genome = Poliovirus Self-complementary sequences within gene coding sequences = Retroviruses Internal Ribosome Entry Site (IRES) = Poliovirus Pseudoknot formation = Retroviruses

Match the following terms with their corresponding definitions:

Stem-loop = A secondary structure in RNA formed by complementary base pairing within a single RNA molecule. Pseudoknot = A complex RNA structure formed by the interaction of two stem-loops. IRES = A sequence in RNA that allows ribosomes to bind and initiate translation without a 5' cap. Frame-shift = A change in the reading frame during translation, resulting in a different amino acid sequence.

Match the following authors with their respective virology textbooks:

<p>Carter &amp; Saunders = Virology: Principles &amp; Applications Lostroh = Molecular and Cellular Biology of Viruses Howley, Knipe &amp; Whelan = Fields Virology</p> Signup and view all the answers

Match the following publishers with their respective virology textbooks:

<p>Wiley Press = Virology: Principles &amp; Applications CRC Press = Molecular and Cellular Biology of Viruses Wolters Kluwer = Fields Virology</p> Signup and view all the answers

Match the following features with their corresponding viral families:

<p>Ribosomes bind RNA despite lack of 5' cap = Poliovirus Ribosome slipping during translation = Retroviruses Translation initiation independent of a 5' cap = Poliovirus Extended gene coding capacity = Retroviruses</p> Signup and view all the answers

Match the following viruses with their respective host organisms.

<p>Foot &amp; mouth disease virus = Animals Lambda (l ) bacteriophage = Bacteria Cauliflower mosaic virus = Plants Human Immunodeficiency Virus = Humans</p> Signup and view all the answers

Match the following viruses with their respective genome types.

<p>Human Immunodeficiency Virus = RNA Lambda (l ) bacteriophage = DNA Turnip yellow mosaic virus = RNA Foot &amp; mouth disease virus = RNA</p> Signup and view all the answers

Match the following viral characteristics with their corresponding classification categories.

<p>Presence of an envelope = Structure of the virus capsid Gene expression strategy = Molecular composition of the genome Genome sequence similarity and phylogeny = Infection pathogenicity Host range = Virus classification and taxonomy</p> Signup and view all the answers

Match the following viruses with their primary mode of transmission.

<p>Measles = Respiratory droplets SARS = Respiratory droplets Foot &amp; mouth disease virus = Contact with infected animals Human Immunodeficiency Virus = Bodily fluids</p> Signup and view all the answers

Match the following viruses with their respective disease symptoms.

<p>Foot &amp; mouth disease virus = Blisters on the mouth, hooves, and teats Cauliflower mosaic virus = Mosaic patterns on leaves Measles = Rash, fever, cough, and runny nose Human Immunodeficiency Virus = Weakened immune system, increased susceptibility to infections</p> Signup and view all the answers

Match the following viral genome properties with their relevant descriptions:

<p>Composition = DNA or RNA, single or multiple 'chromosomes' Conformation = single or double stranded, circular or linear Gene coding strategy = on both or one strand, positive, negative, or ambi-sense Gene copy number = haploid, merodiploid, diploid</p> Signup and view all the answers

Match the following viral genome features with their relevant examples:

<p>Cellular histones = Papillomaviruses, Herpesviruses Viral proteins = Influenza polymerase and nucleoproteins</p> Signup and view all the answers

Match the following replication strategies with their respective descriptions:

<p>Rolling circle = A circular DNA molecule is replicated by nicking one strand and using the 3' end as a primer Strand displacement = A new strand is synthesized using the old one as a template, displacing the old strand Bidirectional (theta) = Replication proceeds in both directions from a single origin Unidirectional = Replication proceeds in one direction from a single origin</p> Signup and view all the answers

Match the following aspects of viral gene expression with their descriptions:

<p>Promoters = Regulatory sequences that control gene transcription Co-ordinated regulation = Several genes are regulated by shared promoters, common in small viral genomes Independent regulation = Most genes have their own promoters, common in larger viral genomes</p> Signup and view all the answers

Match the following terms related to viral gene coding strategy with their definitions:

<p>Gene-sense, positive-sense = The nucleotide sequence of the coding region is the same as mRNA Anti-sense, negative-sense = The nucleotide sequence of the coding region is complementary to mRNA</p> Signup and view all the answers

Match the following viral genome features with their respective examples:

<p>Origin of replication (ori) = Sequences that initiate DNA replication Promoters = Sequences that regulate gene expression Co-ordinated regulation = Papillomaviruses, Hepatitis B virus, Human Immunodeficiency virus (HIV) Independent regulation = Herpesviruses, Poxviruses</p> Signup and view all the answers

Match the following viruses with their respective genome characteristics:

<p>Papillomaviruses = Circular dsDNA Herpesviruses = Linear dsDNA Influenza viruses = Segmented ssRNA HIV = Diploid ssRNA</p> Signup and view all the answers

Match the following viral proteins with their functions:

<p>Influenza polymerase = Synthesizes viral RNA Nucleoproteins = Bind to viral RNA and protect it from degradation Adenovirus terminal protein = Acts as a primer for DNA replication Poliovirus VPg protein = Allows binding to ribosomes for translation</p> Signup and view all the answers

Flashcards

Virus Classification

Systematic categorization of viruses based on characteristics such as genome and structure.

ICTV

International Committee on the Taxonomy of Viruses; the body that classifies viruses.

Viral Genome Composition

The molecular structure of a virus's genetic material, which can be DNA or RNA.

Capsid Structure

The protein shell surrounding a virus, important for its shape and protection.

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Host Range

The spectrum of hosts a virus can infect, including specific species and cell types.

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Virus Composition

Viruses can have DNA or RNA, with single or multiple chromosomes.

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Gene Coding Strategy

Viruses can code on one or both strands, and can be positive, negative, or ambi-sense.

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Positive-sense RNA

RNA that acts like mRNA and can be directly translated.

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Negative-sense RNA

RNA that needs to be converted to positive-sense RNA before translation.

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Replication Origin (ori)

All virus genomes must have at least one origin of replication.

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Replication Strategies

Viruses adopt various methods such as rolling circle or bidirectional replication.

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Promoter Functions

Virus genomes must have promoters to regulate gene expression.

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Coordination in Small Viruses

Small viruses often coordinate regulation across multiple genes using shared promoters.

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IRES

Internal Ribosome Entry Site; a RNA structure allowing ribosome binding without a 5' cap.

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Pseudoknot

A structure formed by self-annealing sequences in RNA that aids in translation.

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Ribosomal slippage

A translational mechanism where ribosomes slip during reading, extending coding capacity.

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Self-complementary sequences

Nucleotide sequences in RNA that can pair with themselves to form structures.

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Frameshift mutation

A type of mutation caused by ribosomal slippage resulting in an altered gene sequence.

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Viruses

Microorganisms that cannot reproduce independently; they need host cells.

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Obligate Intracellular Parasites

Viruses that must invade living cells to replicate.

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Characteristics of Viruses

Not alive, do not grow, do not divide, made of proteins, nucleic acids and sometimes envelopes.

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Virion

Complete virus particle that consists of genetic material and a protective coat.

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Capsid

Protein shell of a virus that protects the genome.

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Nucleocapsid

Structure formed by the capsid and the viral nucleic acid it protects.

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Virus Glycoproteins

Proteins on the virus surface, used for binding to host cells.

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Viral Envelope

Lipids surrounding some viruses, derived from the host cell membrane.

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Helical Capsids

Capsids shaped like hollow cylinders that often consist of a single type of protein.

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Icosahedral Capsids

Capsid structure with 20 triangular faces, often appearing spherical.

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Replication of Viruses

Viruses duplicate their components and assemble new virions, not dividing like cells.

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Virus Genome

The genetic material of a virus, can be either DNA or RNA.

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Common Virus Examples

Examples include Polio, HIV, and Herpes, each with unique capsid structures.

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Antibiotic Resistance in Viruses

Viruses are not affected by antibiotics, which treat bacterial infections.

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T4 Bacteriophage Structure

A virus with both icosahedral (head) and helical (tail) structures.

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Study Notes

Viruses and Virology Overview

  • Viruses infect all cellular life (human, animal, plant, bacteria, yeast, fungi)
  • Viruses are classified based on various characteristics including; molecular composition of the genome, structure of the virus capsid, presence of an envelope, gene expression strategy (producing virus proteins), host range (cell tropism), infection pathogenicity, and genome sequence similarity and phylogeny.
  • The classification system includes Realm, Kingdom, Phylum, Class, Order, Family, Genus, and Species

Virus Structure and Components

  • Viruses have similar components to cells, including glycoproteins (spikes/peplomers, bind to cell entry), a membrane (envelope), and a genome (DNA or RNA).
  • Proteins in viruses include tegument/matrix, capsid, nucleocapsid, and enzymes (carried inside virion or encoded by genome).
  • Viral structural proteins form capsids, which are symmetrical arrangements of the proteins; typical shapes are helical, icosahedral, rod-shaped, and cone-shaped.
  • Icosahedral capsids have 20 triangular sides and appear spherical, made of 1-4 different capsid proteins (papillomavirus, poliovirus, herpesviruses, Hepatitis B, and HIV have 2,4,10,1, and 1 capsid proteins respectively).
  • Helical capsids form hollow cylinders, often using similar single protein many times and wrapping around the genome (Tobacco mosaic virus, rabies virus and Marburg/Ebola virus).
  • Some viruses have complex structures (T4 bacteriophage) combining icosahedral and helical structures.
  • Some viruses have an envelope that surrounds the capsid, made of lipids and protein layers.
  • Virus glycoproteins are embedded in the envelope and bind to cells for entry. Viral proteins show diversity in structure and function, binding genomes, providing replication primers, or binding ribosomes.

Virus Genomes

  • Virus genomes comprise diverse sizes, compositions, conformations, gene coding, and genome copy number (both DNA and RNA based single or double stranded forms.)
  • Viral genomes may use unique sequences for protein synthesis in ways like self-annealing into stem-loops, ribosomes binding to RNA without 5' caps, and frame-shift ribosome slippage to increase gene capacity.

Virus Replication

  • All virus genomes contain at least one origin of replication (ori).
  • Replication strategies include rolling circle, bidirectional (theta), unidirectional, and strand displacement mechanisms.
  • All viruses ultimately replicate two complementary nucleic acid strands, even if the genome is single-stranded.

Gene Regulation

  • Small virus genomes generally use coordinated gene regulation with shared promoters
  • Larger virus genomes usually use independent gene regulation with separate promoters for each gene.

Additional Info

  • Common viral misunderstandings clarify that viruses are not cells, not alive (require host cells to replicate), don't grow, don't divide (but replicate), and are not susceptible to antibiotics.
  • Suitable virology textbooks for learning include Carter & Saunders, Lostroh, and Howley, Knipe & Whelan.

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