Question

In an experiment, a common tobacco mosaic virus (TMV) and its mutant strain ‘HR’ were used to prepare hybrid particles with ‘HR’ nucleic acid and ‘TMV’ protein coat. These hybrids were mixed with antibodies against ‘HR’ strains. If this mixture is applied to plant materials, it will result in
(a) Loss of infectivity of virus particles due to inactivation of nucleic acid
(b) Loss of infectivity due to inactivation of a protein coat
(c) Intact infectivity because the only coat is neutralized
(d) Unchanged infectivity because neither nucleic acid nor protein coat is neutralized

Answer 1

Hint: With the aid of the above-discussed transformation experiment and bacteriophage infection, it was shown that the genetic material is DNA. Experiments performed with the tobacco mosaic virus (TMV) presented the first evidence that RNA also has the capacity to bear genetic material.

Complete answer:
TMV and its mutant strain 'HR' were used in the given experiment to prepare hybrid viral particles with Nucleic acid-HR strain and Protein coat-TMV.
We know that a viral particle transmits its genetic material, i.e. nucleic acid, into the host when it infects another host. If the mixture of hybrid viral particles and HR strain antibodies is mixed, the HR strain antibodies can neutralize the nucleic acid of the HR strain, resulting in the loss of virus particle infectivity due to the inactivation of the nucleic acid.

Additional information: Techniques for separating TMV particles into RNA and proteins were first created. Later on, it could be shown that RNA alone could cause infection by using RNA and proteins separately in infection tests. In the protein fraction, such property was not found. Using RNA from one strain and protein from another strain, chimeric virus particles may also be synthesized. These chimeras had serological characteristics of the strains from which protein was obtained, but they were identical in other characteristics to the other strains from which RNA was used.
So, the correct answer is ‘(a) Loss of infectivity of virus particles due to inactivation of nucleic acid’.

Note: The Tobacco mosaic virus (TMV) in the genus Tobamovirus is a positive-sense single-stranded RNA virus species that infect a wide range of plants, especially tobacco and other Solanaceae family members. Characteristic patterns, such as "mosaic"-like mottling and discoloration on the leaves (hence the name) , are caused by the infection.