Viruses

Parts of a Virus

Nucleic acid (DNA or RNA), capsid, nucleocapsid, envelope, spike proteins, enzymes.

Nucleic Acid

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

Capsid

Protein coat that protects the genetic material of a virus.

Nucleocapsid

Combination of the capsid and the genome (nucleic acid) together.

Envelope in Viruses

Lipid membrane derived from the host cell, present in some viruses.

Spike Proteins

Surface proteins on viruses used for attachment to host cells.

Enzymes in Viruses

Proteins sometimes present in viruses, like reverse transcriptase in retroviruses.

How Viruses are Visible

Viruses cannot be seen with light microscopes but can be observed using electron microscopy.

Plaque Assays

Method to detect viruses by observing clear zones of cell death in cultures.

Molecular Methods to Detect Viruses

Techniques like PCR used to indirectly measure viral presence through infected cells.

Lytic Cycle

An active destruction cycle where the virus hijacks host machinery to make new viruses, leading to host cell lysis.

Lysogenic Cycle

A dormant cycle where viral DNA integrates into host DNA and replicates along with it without causing immediate damage.

Key Difference between Lytic and Lysogenic Cycles

Lytic cycle involves immediate replication and cell death; lysogenic cycle involves dormant integration and delayed activation.

Mechanism of Enveloped Virus Formation

Involves insertion of viral proteins into host membrane, budding out with a part of the host membrane as the viral envelope.

Examples of Enveloped Viruses

Includes influenza and HIV.

Role of Host Cell in Virus Replication

Host cell machinery is hijacked for the replication of viral DNA/RNA and proteins.

Trigger for Lytic Cycle from Lysogenic State

Can be triggered by stress or UV light, leading to activation of dormant viral DNA.

Observing Infected Cells

Used as an indirect method to detect the presence of viruses.

Structure of a Simple Virus

Consists of nucleic acid and a protein capsid.

Lytic Cycle Steps

Attachment to host cell, injection of genetic material, hijacking of host machinery, assembly of new virions, lysis of host cell.

What happens during Lysis of Host Cell?

The host cell bursts, releasing many newly formed virus particles.

Prophage in Lysogenic Cycle

Viral DNA integrated into the host DNA during the lysogenic cycle.

Virus Budding Mechanism

The process where a virus leaves the host cell by taking part of the host's lipid membrane.

Host Cell Made Components

Coat proteins and nucleic acid are made using the host's cellular resources in the lytic cycle.

Immediate Effect of Lytic Cycle

Immediate replication of the virus and subsequent cell death.

Function of Viral Spike Proteins

Used primarily for attaching the virus to specific receptors on host cells.

Observation Technique for Virus Detection

Electron microscopy is used to visualize viruses directly.

Lysogenic Cycle Duration

The viral DNA can remain dormant for long periods within the host cell.

 viral particles produced during Lytic Cycle

Numerous new virus particles are created before the host cell lysis.

Effects of Integration in Lysogenic Cycle

Host cell replicates as normal, copying the integrated viral DNA.

Example of a Lytic Virus

Bacteriophage T4 is a classic example of a lytic virus.

Differences in Host Interaction

Lytic viruses lead to cell death, while lysogenic viruses allow host survival for periods.

Example of a Lysogenic Phage

Lambda phage (λ phage) is a well-known example of a lysogenic virus.

Role of Reverse Transcriptase

An enzyme used by retroviruses to transcribe their RNA into DNA.

Viral Lifecycle Importance

Viral life cycles dictate how a virus interacts with its host and propagates.

Cellular Impact of Lytic Virus

Cell destruction leads to symptoms and viral spread.

Visualizing Virus Size

Viruses are typically in the nanometer size range and require electron microscopy for visualization.

Importance of Viral spike proteins

They are crucial for the infection process as they mediate the attachment of the virus to host cells.

How do enveloped viruses form?

They bud from the host cell, acquiring part of the cell membrane as their envelope.

Microscope Type for Viral Study

Electron microscopes are essential for studying virions due to their small size.

Viruses vs. Pathogenic Bacteria

Viruses lack cellular structure and can't self-replicate without a host.

Cells impacted by Lytic Cycle

Host cells are rapidly destroyed leading to cell lysis.

Example of Virus with Enveloped Structure

HIV is an example of an enveloped virus.

Integration of Viral Genome

Lysogenic phase allows the viral genome to integrate seamlessly into host DNA.

Implications of Lytic Cycle

Promotes fast replication and potential spread but requires immediate host cell death.

Role of Electron Microscopy

Essential for resolving structures at the virus level, which are not visible with ordinary light.

Potential Triggers for Lysogenic Activation

Stress factors or radiation (like UV) can activate the transition to the lytic cycle.

Nature of Viral Envelopes

Composed of host cell lipids, these envelopes can influence viral infectivity.

Nucleic Acid Types in Viruses

Viruses can have either DNA or RNA as their nucleic acid, not both.

Capsid Function

Protects the viral genome and delivers it to the host cell.

Viral Lifecycle Overview

Involves attachment, entry, replication, assembly, and exit from host cells.

Epidemiological Impact of Lytic Viruses

They contribute to disease and outbreak patterns through host cell destruction.

Measurement of Viral Load

Plaque assays can estimate the concentration of viruses in a sample.

Transmission Mechanism of Enveloped Viruses

They typically spread through bodily fluids due to their lipid membranes.

Clinical Importance of Enveloped Viruses

Understanding enveloped viruses aids in developing vaccines and antiviral treatments.

Consequences of Viral Integration

Can lead to cancers or other diseases depending on the host and type of viral integration.

Experimental Techniques for Virology

PCR and plaque assays are common methods for studying viruses.

Lysogenic Reversion Potential

Lysogenic viruses can revert to the lytic cycle under certain conditions.

Retrovirus Example

HIV is an example of a virus that utilizes reverse transcriptase.

Host Mechanisms against Viral Infection

The immune system plays a crucial role in defending against viral infections.

Behavior of Enveloped Viruses

They may exit without killing the host cell, allowing persistent infections.

Viral Pathogenesis

Lytic viruses often cause acute diseases marked by rapid symptoms.

Research Techniques in Virology

Electron microscopy, PCR, and plaque assays are fundamental to viral research.