In the DNA double helix, G and A form complementary base pairs with C and T, respectively. The G=C base pair is formed by making three hydrogen bonds, so it is more stable than the A-T (or A-U in RNA) base pair with only two hydrogen bonds.
In 2002, Hurst and Marchant reported that the optimal growth of prokaryote at higher temperatures is strongly related to the G=C base pair content in functional RNA molecules, but not to that in DNA double helix. More recent study conducted by Zheng and Wu revealed that the G=C base pair content levels of the coding/non-coding regions of certain genes are correlated with the temperature range conditions of prokaryotic organisms.
In biotechnology, the binding affinity of DNA primers used in PCR and antisense oligonucleotides used in knockdown experiments and therapeutics to the complementary strands can easily be improved by increasing the G=C base pair content.
Reference:
- Hurst LD, Merchant AR. High Guanine-Cytosine Content Is Not an Adaptation to High Temperature: A Comparative Analysis Amongst Prokaryotes. Proc Biol Sci. 268, 493-497 (2001).
- Zheng H, Wu H. Gene-centric Association Analysis for the Correlation Between the Guanine-Cytosine Content Levels and Temperature Range Conditions of Prokaryotic Species. BMC bioinformatics, 11, S7 (2010).