3 public questions tagged with this topic.
Adenine is a purine, characterized by a two-ring structure, while thymine, cytosine, and uracil are pyrimidines.
Ref: NCERT Class 11 Biology Chapter 9: Biomolecules Nucleic Acids - DNA RNA Structure and Functions
Purines and pyrimidines normally exist in keto-amino tautomers that form canonical Watson-Crick pairs G-C and A-T. Rare enol-imino tautomers relocate hydrogen bonding donors and acceptors altering pairing face. A transient tautomeric shift converts guanine to enol form presenting hydrogen bonding pattern similar to adenine, allowing stable pairing with thymine instead of cytosine. If uncorrected before next round of replication, replication past this mispair fixes G-C to A-T transition mutation. Phenomenon underlies spontaneous point mutations and explains mutagenesis by base analogs like bromouracil.
Ref: Watson JD et al., Molecular Biology of the Gene, 7th ed., Chapter 9: Rare tautomeric shifts and mispairing
Adenine and Guanine is the scientifically accurate answer to this question. Within the study of Nucleic Acid, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of Adenine and Guanine directly address what is being asked. Among the other options, Adenine and Thymine, Cytosine and Guanine, and Uracil and Thymine do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.
Ref: Campbell Biology, Urry et al., 12th Ed.
