Question

Which of the following viruses has DNA?
A. Tobacco mosaic virus
B. Cauliflower mosaic virus
C. Tomato mosaic virus
D. Potato mosaic virus

Answer 1

A virus is a microscopic infectious agent. They can replicate only inside the living host. Viruses infect all types of life forms including plants, animals and microorganisms. More than $9,000$ species of virus have been identified in the environment. Virus has a protective outer capsid responsible for virulence in host organisms. Their genetic material is made up of either DNA or RNA. Most of the viruses containing RNA have its genetic material.

Complete explanation:
Option A Tobacco mosaic virus: Tobacco mosaic virus is a single stranded virus made up of RNA. It infects a wide range of plants, particularly tobacco and other members of the Solanaceae family. The infection causes characteristic mosaic-like patterns and discoloration on the leaves of the plants.
Option A is incorrect.
Option B Cauliflower mosaic virus: Cauliflower mosaic virus belongs to the genus Caulimovirus, which is one of the six genera in the family Caulimoviridae. The genetic material here is DNA instead of RNA. Cauliflower mosaic virus mostly infects the plants of Brassicaceae family like cauliflower and turnip but some are also able to infect Solanaceae species.
Option B is correct.
Option C Tomato mosaic virus: Tomato mosaic virus is a plant virus that affects tomatoes and many other plants. They are distributed worldwide. The affected tomato plants show mottling, discoloration and have blister-like appearance. The virus has RNA as its genetic material.
Option C is incorrect.
Option D Potato mosaic virus: Potato mosaic virus is a plant pathogenic virus belonging to the family Potyviridae. Potato mosaic virus has multiple pathogenic strains. It greatly affects the tuber quality and yield of potatoes. It is an RNA virus.
Option D is incorrect.

Hence, Option B. Cauliflower mosaic virus is the correct answer.

Note:
Plant viruses are a type of intracellular parasites that do not have any machinery to replicate without a host. Plant viruses are pathogenic to all higher plants. The plant viruses are usually rod-shaped, with a protective protein tube surrounding the viral genome. They mostly don’t have an envelope like animal viruses. Majority of viruses have an RNA genome. Plant defences against viral infection include production of protein and siRNA to suppress the virulence.