Explanation:In a bacteriophage, the DNA is located in the head of the virus. The head is a protein structure that encases the viral DNA, protecting it until it can be injected into a host bacterium.

Explanation:Chrysanthemum stunt disease and potato spindle tuber disease are caused by viroids, which are small, circular RNA molecules that can infect plants and cause disease. Unlike viruses, viroids do not have a protein coat.

Explanation:Viruses are commonly transmitted in plants through sucking insects such as aphids and whiteflies. These insects act as vectors, transferring the virus from infected to healthy plants.

Explanation:Prions are infectious agents composed solely of proteins. They are responsible for several neurodegenerative diseases in mammals, including Creutzfeldt-Jakob disease and mad cow disease.

Explanation:W.M. Stanley was the first to crystallize the Tobacco Mosaic Virus (TMV), demonstrating that viruses could be purified and studied in a crystalline form. His work earned him the Nobel Prize in Chemistry.

Explanation:Felix d’Herelle conducted detailed studies on bacteriophages, viruses that infect bacteria. His work provided significant insights into the nature and behavior of bacteriophages.

Explanation:Smallpox is caused by the Variola virus. It was a highly contagious and deadly disease before being eradicated by a global vaccination campaign.

Explanation:Viruses can have either RNA or DNA as their genetic material, but not both. This genetic material is enclosed within a protein coat and is essential for the virus’s ability to infect host cells and replicate.

Explanation:Polio is caused by the poliovirus, which infects the nervous system and can lead to paralysis. The disease has been largely eradicated through widespread vaccination efforts.

Explanation:The Tobacco Mosaic Virus (TMV) has RNA as its genetic material. This was one of the first viruses to be discovered and studied, providing significant insights into the nature of viral genetic material.