Question

Fraenkel Conrat demonstrated that RNA is genetic material in
A. HIV
B. CMV
C. TMV
D. Mouse sarcoma

Answer 1

Hint: In living organisms, the genes are responsible for transfer of genetic material from one generation to the generation and they work to control the hereditary characters. The component or the substance that acts as genetic material must fulfill some basic criteria.

Complete answer:
The genetic material is the fundamental unit in the genotypic and phenotypic expression of an organism. A genetic material must be able to accumulate mutation in addition to recombination to bring about versatility or variation to the gene pool of the organism. Most of the genetic material identified are DNA and RNA. The plant viruses generally contain RNA as their hereditary material. The first proof about RNA being the hereditary material and also capable of transmitting genetic data comes from experiments with TMV or tobacco mosaic virus. The experiments were done by Fraenkel Conrat.

TMV is a small virus that exists as a single molecule of RNA enclosed in a capsule of cylindrical protein coat. Fraenkel Conrat created certain hybrid strains of this virus and separated protein coats from them. All the members of different generations were then administered on the tobacco plant showed that the progenies were always identical to the parents. Thus, RNA is the hereditary material in the TMV was proved. RNA was detected in a number of bacteriophages after demonstration of the genetic existence of RNA in TMV. Fraenkel Conrat conducted his experiments on a plant virus in order to demonstrate the existence of RNA as genetic material. This plant virus can infect a wide variety of plants involving tobacco and some of the members of the Solanaceae family.

HIV is a retrovirus, which means that it bears a single-stranded RNA as its genetic material rather than a double-stranded DNA in human cells. The retroviruses are also known to contain enzymes reverse-transcriptase, which allow copying of RNA to DNA and using the DNA or RNA "copy" to infect cells or human beings.

The largest genome of a known human virus is human cytomegalovirus (HCMV), which is two hundred and thirty six kilo-base pairs (kbp). The genome is a linear, dual-stream DNA molecule made up of two distinct regions, flanked by inverted repeats

The complete sequence of nucleotides of a molecularly cloned mouse viral sarcoma DNA with biologic infection was identified. It contains two long repeats at each terminal, and it has the coding ability of the whole gag gene, pol-gene portions and the whole transforming gene.

Hence, The correct answer is option (C).

Note: RNA is the genetic source of most plant viruses. Fraenkel Conrat carried out tobacco mosaic virus (TMV) experiments to prove that RNA functions as genetic material in some viruses. TMV is a small virus consisting of a single RNA molecule enclosed in a cylinder shaped protein shell. Fraenkel-Conrat disassembled the virus from its noninfectious protein coat and nucleic acid components in a series of experiments and then reassembled these components to achieve the recomposition of the virus in full infectious form. The infectious nature and other characters of the virus were successfully found in different generations of progeny.