Read the passage given below and answer the following question.
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the two types of nucleic acids found in living systems. DNA acts as the genetic material in most of the organisms. RNA though it also acts as a genetic material in some viruses, mostly functions as a messenger. RNA has additional roles as well. It functions as adapter, structural, and in some cases as a catalytic molecule. The chemical structure of a polynucleotide chain (DNA or RNA). A nucleotide has three components – a nitrogenous base, a pentose sugar (ribose in case of RNA, and deoxyribose for DNA), and a phosphate group. There are two types of nitrogenous bases – Purines and Pyrimidines.
In which of the following organisms does RNA act as the genetic material?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Tobacco Mosaic Virus
DNA is the genetic material of most organisms. Some viruses are an exception: in them, RNA is the genetic material. The book names Tobacco Mosaic Virus (TMV) and a bacteriophage as examples.
Option (1) Escherichia coli — Incorrect. Escherichia coli is a bacterium. Like all cellular organisms, it has DNA as its genetic material.
Option (2) Tobacco Mosaic Virus — Correct. Tobacco Mosaic Virus, which infects tobacco plants, carries RNA as its genetic material.
Option (3) Both of the above — Incorrect. Only TMV has RNA as its genetic material. E. coli has DNA, so “both” is wrong.
NCERT Extract:
Properties of Genetic Material (DNA versus RNA) – “From the foregoing discussion, it is clear that the debate between proteins versus DNA as the genetic material was unequivocally resolved from Hershey-Chase experiment. It became an established fact that it is DNA that acts as genetic material. However, it subsequently became clear that in some viruses, RNA is the genetic material (for example, Tobacco Mosaic viruses, QB bacteriophage, etc.).”