Question

Which of the following shows coiled RNA strand and capsomeres?
A.Polio virus
B.Tobacco mosaic virus
C.Measles virus
D.Retro virus

Answer 1

A capsomere is the subunit of capsids which is an outer protein coat that protects the genetic material of the viruses. The self-assembling of capsomeres leads to the formation of capsids.

Complete answer:
Tobacco mosaic virus contains a single-stranded RNA molecule as its genetic material which has positively sensed coil. The virus has a rod-shaped appearance. It consists of an outer cover known as the capsid, consisting of capsomeres which are 2130 in numbers. The protein is assembled into a rod-like helical structure around the genetic material. The virus infects plants belonging to the family Solanaceae such as Tobacco.

Figure: Tobacco mosaic virus structure
Considering other given options:
Poliovirus, even though it consists of capsid around the genetic material, is not divided further into capsomeres. Its genetic material is a single-stranded RNA.
Measles virus is a spherical virus possessing a helical ribonucleoprotein core.
Retrovirus has an outer glycoprotein cover, which facilitates binding to the host cells. Within it the genetic material is present.
So, the correct answer is option B that is ‘Tobacco mosaic virus’.

Note: The various symptoms associated with tobacco mosaic virus infections are stunted growth, a mosaic-like pattern consisting of green or light yellow colors on the leaves, yellow-colored streaking and spotting on the leaves, malformed leaves, yellowing of veins. The transmission of the virus occurs through contact between the plants or through the farmers. It mainly infects the chloroplasts of the leaves. The virus decreases the amount of chlorophyll produced thereby reducing the extent of photosynthesis happening, contributing to reduced nutrition, leading to stunted growth in plants.