The invention concerns a method for analyzing nucleic acids using a small-size probe array comprising deoxyinostines (dI) instead of deoxyguanogines (dG). The invention also concerns such probe arrays and their use in methods for detecting and/or quantifying target oilgonucleotides present in DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) molecules in a sample, in particular mRNA editing rate of the serotonin 5-HT.sub.2C receptor (5-HT.sub.2C-R). The invention further concerns a biochip or a reactor in liquid medium comprising such probe arrays as well as their uses, in particular for detecting and/or identifying genetic polymorphisms or for determining an mRNA editing rate, whether it is that of a 5-HT.sub.2C-R mRNA or any other RNA capable of being edited. The invention also concerns a method based on the isolation of a single strand conformation polymorphism (SSCP) enabling under specific analysis conditions the editing profile and/or rate of an mRNA capable of being edited to be obtained, as well as a method for diagnosing diseases or susceptibility to diseases associated with the degree of edition of an mRNA. Finally, the invention concerns a method for selecting compounds capable of modulating mRNA editing rate, in particular that of 5-HT.sub.2C-R, as well as the use of such compounds for preparing a pharmaceutical composition for treating organic fluid.