Which of the following are Pyrimidine bases?: (A) Adenine and Guanine, (B) Guanine and Cytosine, (C) Cytosine and Adenine, (D) Thymine and Cytosine
Answer is D. In DNA and RNA, Pyrimidine bases form hydrogen bonds with their complementary purines. Thus, in DNA, the purines adenine (A) and guanine (G) pair up with the pyrimidines thymine (T) and cytosine (C), respectively. In RNA, the complement of adenine (A) is uracil (U) instead of thymine (T), so the pairs that form are adenine: uracil and guanine: cytosine. Ref: Rodwell V.W. (2011). Chapter 32. Nucleotides. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e