Which is NOT true for a molecule that can act as a genetic material?

The correct answer is Option (2) → It should be chemically and structurally unstable

Option (1) It should be able to generate its replica — True for a genetic material. It must copy itself (replication) so that each new cell gets it.

Option (2) It should be chemically and structurally unstable — Not true for a genetic material. It must be stable, so that it is not changed with age or with the stage of the life cycle. This is why DNA, more stable than RNA, is the main genetic material.

Option (3) It should provide the scope for slow changes that are required for evolution — True for a genetic material. NCERT lists the scope for slow changes (mutation) as criterion (iii). These slow changes give the variation on which evolution acts, so this is a true property.

Option (4) It should be able to express itself in the form of "mendelian character' — True for a genetic material. Its information must show up as characters in the organism.

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’.”