Higher GC-content in nucleic acid duplex structures correlates with which of the following?

• A. Lower stability and melting temperature
• B. More stable duplex and higher melting temperature
• C. Less susceptibility to mutations
• D. Decreased binding affinity

Answer: (B)

The correlation between higher GC-content in nucleic acid duplex structures and increased stability and higher melting temperature is rooted in the structural properties of nucleic acids. GC pairs form three hydrogen bonds, whereas AT pairs only form two. This difference in hydrogen bonding gives GC-rich regions greater thermal stability. As a result, the higher the GC-content in the DNA or RNA strand, the more energy is required to separate the strands, leading to a higher melting temperature.

In practical terms, when subjected to increasing temperatures, duplexes with higher GC-content will remain intact longer than those with lower GC-content. This characteristic is particularly important in biological processes such as DNA replication and transcription, where the stability of the nucleic acid strands plays a crucial role in functionality. Thus, the observation that higher GC-content correlates with more stable duplexes and higher melting temperatures is well-supported by biochemical principles.