Q. Which one of the following pairs of nitrogenous bases of nucleic acids, is wrongly matched with the category mentioned against it?
A) Guanine, Adenine - Purines
B) Adenine, Thymine - Purines
C) Thymine, Uracil - Pyrimidines
D) Uracil, Cytosine - Pyrimidines
Explanation
The two DNA chains are held together by hydrogen bonds between their nitrogenous bases. Adenine (a), a purine of one chain lies exactly opposite thymine (T), a pyrimidine of the other chain. Similarly, cytosine (c), a pyrimidine lies opposite guanine (G), a purine. Three hydrogen bonds occur between cytosine and guanine (C ≡ G) at positions 1′, 2′, and 6′ and two hydrogen bonds between adenine and thymine (A = T) at positions 1′ and 6′.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.