Question

TMV has a size of
A. 50nm$\times$10nm
B. 100nm$\times$20nm
C. 300nm$\times$18nm
D. 500nm$\times$24nm

Answer 1

Tobacco mosaic virus is a positive-sense ssRNA virus species belonging to genus Tobamovirus which infects plants (especially tobacco). This infection causes mosaic mottling and discoloration of leaves.

Complete answer:
TMV, also referred to as Tobamovirus, is a rod-shaped virus with RNA surrounded by a coat of protein that causes mosaic-like symptoms in plants. These symptoms are characterized by mottled patches of green or yellow color on the leaves of infected plants. The virus causes abnormal cellular function that sometimes doesn't kill the plant but stunts growth. Such plants have brittle stems, abnormally small, curled leaves, and unripened fruit.
Tobacco mosaic virus is capable of infecting many varieties of plants, not just tobacco plants. TMV is spread through small wounds caused by handling insects, or broken leaf hairs that result from leaves rubbing together. The virus attaches to the cytomembrane, injects its RNA into the host cell, and forces the host cell to provide new viral RNA and proteins. The viral RNA and proteins assemble into new viruses and infect other cells by passing through small openings called plasmodesmata.
Structure of mosaic Virus (TMV):
TMV may be a simple rod-shaped helical virus consisting of centrally located single- stranded RNA (5.6%) enveloped by a protein coat (94.4%). The capsid is created from 2130 molecules of coat protein and one molecule of genomic ssRNA, 6400 bases long. The rod is 3,000 angstrom long and 180 angstrom in diameter. The protein coat is technically called ‘capsid’.
The diameter of RNA helix is 80 angstrom and therefore the RNA molecule lies at 50 angstrom inward from the outermost surface of the rod. The central core of the rod is 40 Å in diameter. Each capsomere has 158 amino acids and a mass of 17,000 Dalton.
The ssRNA is about 3300 angstrom long. The RNA molecule consists of 7300 nucleotides and its mass is 25,000 Dalton.

Therefore, the right option is C, 300nm$\times$18nm

Note:
Plant viruses are used to engineer viral vectors, which are utilized by molecular biologists for inserting genetic material into plant cells. They also act as a source for biomaterials and nanotechnology devices. Thanks to its cylindrical shape, high ratio, self-assembling nature, and skill to include metal coatings into its shell, TMV is a perfect candidate to be incorporated into battery electrodes which might increase the reactive extent by an order of magnitude, leading to a rise within the battery's capacity by up to 6 times compared to planar electrode geometry.