Question

Describe two ways in which the genomes of poliovirus and influenza virus differ. (Sections \(9.8\) and 9.9)

Short answer

Poliovirus has a single-stranded positive-sense RNA genome and is non-segmented, while Influenza virus has a segmented genome consisting of 8 RNA segments.

Step-by-step solution

- Identify Genome Type

The first key difference is the type of genome each virus has. Poliovirus has a single-stranded RNA (ssRNA) positive-sense genome. This means that its RNA can directly serve as mRNA, which is immediately translatable by the host's ribosomes.

- Determine Genome Segmentation

The second difference pertains to the segmentation of the genomes. Influenza virus has a segmented genome consisting of 8 distinct RNA segments, whereas poliovirus has a non-segmented genome. This segmentation in influenza facilitates reassortment, which is one of the mechanisms for generating viral diversity.

Key concepts

Poliovirus genome

The poliovirus genome is fascinating and quite simple in its structure. Poliovirus has a single-stranded RNA (ssRNA) genome. This is known as a positive-sense RNA. Because of this positive-sense orientation, the RNA can directly serve as mRNA. This allows it to be immediately translated by the host cell's ribosomes upon infection.

• Poliovirus's RNA is non-segmented, meaning it is one continuous molecule.
• This structure is efficient for the virus's replication and protein synthesis.

The simplicity of the genome makes it a model organism in virology, helping scientists understand basic principles of viral replication and pathogenicity.

Influenza virus genome

In contrast to poliovirus, the influenza virus has a segmented genome. This genome consists of 8 separate RNA segments.

• Each segment encodes different proteins required for the virus's life cycle.
• The segmentation allows for a higher level of genetic diversity through a process known as reassortment.

When two different influenza viruses infect the same cell, their RNA segments can mix and match, creating new viral strains. This ability is a key reason for the virus's adaptability and is a contributing factor to its pandemic potential.

RNA virus segmentation

Viruses with segmented genomes, like the influenza virus, have a unique evolutionary advantage. Segmentation means that the viral genome is divided into multiple distinct RNA molecules.

• This allows for genetic reassortment, where segments from different viral strains can combine in new ways.
• New viral strains can arise rapidly, leading to increased viral diversity.

This process can result in viruses that evade the immune system or become more infectious. Segmentation is a primary reason why influenza stays a challenging virus to predict and control.

Positive-sense RNA

Positive-sense, single-stranded RNA (ssRNA) viruses, like poliovirus, have RNA that can function directly as mRNA. This capability speeds up the viral replication process as their RNA is ready to be translated into proteins by the host's ribosomes.

• This allows for efficient viral protein production immediately after infection.
• The genome itself acts as a template for viral replication.

Positive-sense RNA viruses can rapidly hijack the host cell machinery, making them effective and often highly contagious pathogens.

Viral diversity

Viral diversity is crucial for understanding the adaptability and evolution of viruses. Different mechanisms contribute to this diversity.

• For segmented viruses like influenza, reassortment enables the mixing of genetic material from different strains.
• For non-segmented RNA viruses like poliovirus, mutations during replication can introduce genetic changes.

These variations help the virus to adapt to new host environments and evade the immune system. Studying viral diversity helps researchers anticipate future viral threats and develop effective vaccines and treatments.