MCQs

DNA viruses contain DNA as their genetic material, whereas RNA viruses contain RNA. A virus never contains both DNA and RNA simultaneously.

Tobacco Mosaic Virus causes mosaic-like discoloration on tobacco and several other plant leaves, reducing crop yield.

Bacteriophages specifically infect bacterial cells by attaching to receptors on the bacterial cell wall.

Rabies virus has a bullet-shaped appearance but internally possesses a helical nucleocapsid.

Adenovirus is a classic example of a naked virus with an icosahedral capsid, making it highly resistant to environmental conditions.

Adenoviruses possess a linear double-stranded DNA genome enclosed in an icosahedral capsid.

Influenza virus infects humans, birds, and several mammals, therefore it belongs to the animal viruses.

Lipid envelopes are easily disrupted by heat, drying, soaps, and detergents, making enveloped viruses less stable outside the host.

Human Immunodeficiency Virus (HIV) is a retrovirus containing single-stranded RNA and the enzyme reverse transcriptase.

Positive-sense ssRNA viruses can be translated immediately by host ribosomes upon entering the host cell.

Hepatitis B virus is a partially double-stranded DNA virus belonging to the Hepadnaviridae family. It replicates through reverse transcription but is classified as a DNA virus.

T4 bacteriophage possesses an icosahedral head, helical tail, and tail fibers, making it the classic example of a complex virus.

TMV infects tobacco and many related plants but cannot infect animal cells because of host specificity.

Naked viruses possess only a nucleic acid core surrounded by a protein capsid and are generally more resistant to environmental conditions.

Viral envelopes originate from host cell membranes and contain viral glycoproteins essential for attachment and entry.

Tobacco Mosaic Virus (TMV) is a classic example of a helical, positive-sense single-stranded RNA virus infecting plants.

Helical viruses have capsomeres arranged helically around the viral nucleic acid, producing a rod-like appearance.

Icosahedral viruses have a highly symmetrical capsid composed of 20 triangular faces, providing maximum stability.

Bacteriophages are viruses that specifically infect bacteria and play important roles in bacterial genetics and biotechnology.