Number Quiz: Basic Arithmetic Questions

Virology

• Virology is the study of viruses.
• Viruses are one of the smallest forms of microorganism and infect animals, plants, and bacteria.
• Viruses cause a wide range of infections in humans, from common colds to AIDS.
• Viruses are metabolically inactive outside susceptible host cells.
• Viruses are obligate intracellular parasites meaning they can only multiply inside living cells.

Novel Properties of Viruses

• Viruses are obligate intracellular parasites of bacteria, protozoa, fungi, algae, plants, and animals.
• Viruses are ultramicroscopic in size, ranging from 20 nm to 450 nm in diameter.
• Viruses are not cells and do not independently fulfill the characteristics of life.
• Viruses are inactive macromolecules outside host cells, but active inside.
• Viruses can form crystal-like masses.
• Virus structure usually consists of a protein shell (capsid) surrounding a nucleic acid core.
• The nucleic acid can be either DNA or RNA but not both in one virus.
• Nucleic acid can be double-stranded DNA, single-stranded DNA, single-stranded RNA, or double-stranded RNA.
• Molecules on the virus's surface determine its high specificity of attachment to host cells.
• Viruses replicate by taking control of the host cell's genetic material and regulating synthesis of new viruses.
• Viruses lack enzymes for most metabolic processes and the machinery for synthesizing proteins.

Resistance of Viruses

• Viruses are heat-labile, inactivated at 56°C within seconds.
• Viruses can be heat-stable at low temperatures.
• Viruses are disrupted by alkaline conditions.
• Viruses are inactivated by UV light, sunlight, and ionizing radiation.
• Some oxidizing agents such as H2S inactivate viruses.
• Antibiotics are ineffective against viruses.
• Viruses are destroyed by alkaline conditions.
• Ultraviolet and X-rays inactivate viruses.

Size and Shape of Viruses

• Viruses range from 20-400 nm in diameter.
• Viruses have various shapes, including spheres, rods, bullets, and bricks.
• The precise geometric symmetry determines virus shape.
• Virus coat (capsid) consists of repeating subunits.
• Viral nucleic acid can be single- or double-stranded DNA or single- or double-stranded RNA.

Viral Structure

• Viral nucleocapsids have two forms of symmetry: icosahedral (capsomers arranged in 20 triangles) and helical (capsomers arranged in a hollow coil).

Viral Proteins

• Capsid proteins protect DNA or RNA from degradation by nucleases.
• Surface proteins mediate virus attachment to host cell receptors.
• Internal viral proteins are structural or enzymes that synthesize viral mRNA.

Viral Envelope

• The viral envelope is a lipoprotein membrane derived from the host cell membrane, with virus-specific proteins.
• Herpesviruses acquire their envelope from the host cell's nuclear membrane.
• Enveloped viruses are more susceptible to heat, drying, detergents, and lipid solvents.

Complex Viruses

• Poxviruses are large DNA viruses that lack a capsid and have layers of lipoproteins.
• Bacteriophages have polyhedral heads, helical tails, and fibers for host cell attachment.

Viral Replication Cycle

• Viruses replicate within host cells, and time required varies.
• Replication follows different pathways depending on viral RNA or DNA nature.

Attachment, Penetration, and Uncoating

• Viral proteins attach to specific host cell receptors.
• Viruses enter cells through direct membrane fusion or endocytosis.
• The viral capsid is removed (uncoating).

Gene Expression and Genome Replication

• Virus replicates a specific process depending on host cell and RNA or DNA type.
• Some viruses follow from DNA to RNA to protein.
• dsDNA viruses.
• ssDNA viruses.
• RNA viruses.

DNA Viruses

• Most DNA viruses replicate in the nucleus.
• Poxviruses replicate in the cytoplasm.

RNA Viruses

• RNA genomes are either dsRNA, +ssRNA, or -ssRNA.
• Some RNA viruses use host enzymes to create a complementary strand.
• Some need a viral RNA polymerase.

Viral Persistence

• Some viral infections continue and persist in hosts for long periods.
• Some become latent or chronic.
• The time to detect the presence of viruses may appear after viral replication.

Cytopathogenic Effects

• Viruses can alter cell shape, size, develop inclusions or form multinucleated cells.
• Viruses cause cell lysis or alter host cell DNA.
• Some viruses can transform cells into cancerous cells.

Diagnosis Of Viral Infections

• Diagnosing viral infections is more complex than bacterial infections.
• Doctors review overall clinical picture.
• Appropriate sample collection.
• Virus detection using cell culture, or characteristic cytopathic effects.
• Antibody tests for an immune response to the virus (serological testing).
• Genetic analysis (PCR).

Antiviral Therapy

• Antiviral drugs are limited compared to antibacterial drugs.
• Antiviral drugs have difficulty targeting virus precisely during cell processes without harming host cells.

Herpesviruses

• Herpesviruses are important human pathogens that often cause latency.
• Herpesviruses are structurally similar. They have a double-stranded DNA genome and lipoprotein envelopes.

Picornaviruses

• Picornaviruses are icosahedral, contain RNA (30%), protein(70%), single-stranded RNA, linear, positive sense.
• Envelope is not present.
• Replication occurs in cytoplasm.

Togaviruses

• Togaviruses are composed of a single-strand RNA + sense genome.
• The virus has a single antigenic type with a single lipoprotein envelope.

Hepatitis Viruses

• Five hepatitis viruses (HAV, HBV, HCV, HDV, HEV) commonly cause liver infection.
• Features vary.

Human Immunodeficiency Virus (HIV)

• HIV causes acquired immunodeficiency syndrome (AIDS).
• HIV infects Helper T-cells and leads to loss of cell-mediated immunity.
• Other cells (like macrophages) containing CD4 proteins can also be infected.
• HIV's genome consists of two identical molecules of single-stranded, positive-polarity RNA.
• Retroviruses have gag, pol, and env and some regulatory genes.

Paramyxoviruses

• Their genomes are not segmented and are composed of negative-sense ssRNA, helical nucleocapsid, and outer lipoprotein envelope.

Assembly and Release

• Components of virions assemble within host cells.
• Virions are released through cell lysis (non-enveloped viruses) or budding (enveloped viruses).

Bacteriophages

• Phages are viruses that infect and replicate within bacteria.
• Their genomes often encode hundreds of genes and replicate within bacterium cytoplasm.

Defective Viruses

• Defective viruses lack essential genetic material, and other viruses provide helper activities.
• Examples include HDV and AAV.

Oncoviruses

• Oncoviruses cause cell transformation and contribute to cellular mutations for cancer.
• Cells grow uncontrollably, and chromosomes cause alterations or indefinite division.

Test your knowledge with this engaging quiz about numbers. Answer questions about counting items, identifying patterns, and performing basic arithmetic operations. Challenge yourself with problems involving pairs and multiplication!