Question #45098

The spontaneous mutation of DNA is often attributed to the transient formation of rare tautomers of nucleobases. Consider the tautomerization of Adenine (A) to its rare imino form ($A^*$) at 298 K and physiological pH. In its standard amino form, Adenine pairs with Thymine (T) via two hydrogen bonds, where N1 acts as an acceptor and N6 acts as a donor. When $A^*$ is incorporated during DNA replication, it forms a stable mispair that preserves the standard purine-pyrimidine Watson-Crick geometry. Which of the following correctly identifies the mispaired nucleobase and the altered hydrogen-bonding roles of N1 and N6 in $A^*$?