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.
Which of the following criteria must a molecule fulfil to act as genetic material?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → All of these.
A molecule can serve as the genetic material only if it meets four criteria. It must copy itself (replication), be chemically and structurally stable, allow slow changes (mutation) for evolution, and express itself as Mendelian characters. DNA meets these better than RNA, so DNA is the genetic material of most organisms.
Option (1) It should be able to generate its replica. — Correct statement, but it is only one of the correct points, so on its own it is not the answer. The genetic material must be able to make its own copy so that each new cell gets the same information. This is replication.
Option (2) It should be stable chemically and structurally. — Correct statement, but it is only one of the correct points, so on its own it is not the answer. The genetic material must be stable, so that it does not change with age or the stage of the life cycle.
Option (3) It should be able to express itself in the form of Mendelian character. — Correct statement, but it is only one of the correct points, so on its own it is not the answer. The genetic material must show its effect as characters that are inherited in Mendelian fashion.
NCERT Extract:
Properties of Genetic Material (DNA versus RNA) – “… A molecule that can act as a genetic material must fulfill the following criteria: (i) It should be able to generate its replica (Replication). (ii) It should be stable chemically and structurally. (iii) It should provide the scope for slow changes (mutation) that are required for evolution. (iv) It should be able to express itself in the form of ‘Mendelian Characters’.”