DNA and RNA Structure Practice Test

A researcher compares two nucleic acid polymers. Polymer X contains ribose sugars and includes uracil among its nitrogenous bases. Polymer Y contains deoxyribose sugars and includes thymine. Both polymers can form complementary base pairs via hydrogen bonding. Which statement best describes how a specific structural difference between X and Y influences their chemical stability at the molecular level?

A researcher synthesizes a short nucleic acid strand with the sequence 5'-AUGC-3'. In solution, it binds tightly to a second strand through hydrogen bonding between complementary bases, forming a short double-stranded region. The binding requires antiparallel alignment of the two strands. Which sequence best represents the strand that will base-pair with 5'-AUGC-3'?