Question

Predominant forms at physiological pH 3. Pyrimidines and purines can exist in alternate forms, or tautomers, shown here. Under common cellular conditions (physiological pH) the most common form of each purine or pyrimidine is shown on the left, and the rare tautomer on the right. Tautomers differ in the placement of hydrogen atoms and double bonds. Consider cytosine and its tautomer, the rare imino form of cytosine. Adenine Cytosine With which nitrogenous base will the imino form of cytosine most likely base pair in a double stranded DNA? Hint: Compare to the typical Watson-Crick base-paring shown below. A. B. C. D. adenine cytosine guanine thymine uracil E Hydrogen bond S'end - Ducks IO IO 19 3' end

Answer 1

Option A is correct.

Adenine in its amino form forms bond with cytosine in imino form.

W -H- Adenine Cytosine limino) (Amino)