The Chargaff’s rule (1:1 stoichiometric ratio of purine and pyrimidine bases) is not followed in organisms having

Correct option is A

✅ (a) ssRNA – Single-Stranded RNA [No Base Pairing] • Chargaff’s rule applies to double-stranded DNA, where adenine pairs with thymine and guanine with cytosine. • In single-stranded RNA, there is no base pairing, hence no 1:1 purine:pyrimidine ratio. • The base composition varies widely and is not complementary.
❌ (b) dsDNA : RNA hybrid • Partially follows base pairing rules — DNA base pairs with RNA (e.g., A-U, G-C). • Still maintains some base complementarity.
❌ (c) dsDNA • Strictly follows Chargaff’s rule due to complementary base pairing.
❌ (d) dsRNA • Though rare, dsRNA molecules follow base pairing (A-U, G-C) and obey a similar rule.