Question

Which nitrogenous base is normally present in RNA

molecules but not in DNA molecules?
(1) adenine
(3) thymine
(2) cytosine
(4) uracil​

Answer 1

RNA contains cytosine and uracil as pyrimidine. DNA has cytosine and thymine.

Answer 2

Answer: In DNA, the pyrimidine cytosine always pairs with the purine guanine, while the pyrimidine thymine always pairs with the purine adenine. RNA does not contain thymine, though, so in RNA adenine pairs with uracil.

Step-by-step explanation: