Questions & Answers

TMV is a
(a) Helical virus
(b) Polyhedral virus
(c) Spherical virus
(d) Binal virus

Answer
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Hint: TMV is known as tobacco mosaic virus which is the first discovered virus based on its structure. It is made up of single-strand RNA and is surrounded by capsid which is made up of protein and it is rod-shaped with a helical arrangement.

Complete Answer:
The tobacco mosaic virus or TMV was first crystallised by Wendell Meredith Stanley in 1935. Tobacco mosaic viruses occur in rod-like elongated form and it is a helical virus. It consists of a single-stranded RNA nucleoid and the nucleoid is covered by a protein coat capsid which is made up of a capsomeres subunit due to this it comes under the class Ribohelica. Its common hosts are tobacco, tomato and other solanaceous plants.
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Additional Information:
Due to the tobacco mosaic virus, the symptoms that arise are mosaic, moulting, necrosis, stunning, leaf curling, and yellowing of plant leaves. It also causes poor yielding, delay ripening of fruit and uneven fruit colour, especially in tomatoes.
It gets transmitted from an infected plant to a healthy plant or from one plant part to another plant by direct contact or indirectly by contaminated tools and infected plant seeds. Internally the transmission takes place through xylem and phloem and from cell to cell by replication and it infected the whole plant from root to tip.

So, the correct answer is 'Helical virus'.

Note:
The unique property of the tobacco mosaic virus is that it does not die with the host plant therefore when a new plant is planted in the soil containing debris of the infected plant the new plant also gets infected. It also survives at extremely high temperatures, therefore, it is hard to control this virus once it starts infecting the plant.